Half-Life (series)/WMG

Wild Mass Guessing concerning the Half-Life games.

The G-Man's employers are Valve Software
The G-Man is the personification of Marc Laidlaw's attempts to keep the story linear. As such, it is the G-Man that is to blame for the weird coincidences that keep Freeman on his feet. As the series progressed, G-Man gained more of a personality and characterization, leading to his replacement by the Fourth Wall breaking Vortigaunts in Episode 1.

The series will end with G-Man taking Gordon to meet his employers, upon which the player will view a video recorded by the staff at Valve, thanking them for playing and doing some minor story exposition. The game will then close. When the player attempts to reopen them, the "New Game" button has been replaced with "New Game+", which features dialogue from Gordon.

As of the events of Half-Life 2, Episode Two, Alyx is carrying Gordon's child.
As the Vortigaunts heal Alyx in Episode Two, they ask Gordon to lend them a hand in stabilizing her. Then the Vorts "weave [his and Alyx's] life forces together," forming a "nearly vortal bond." Also note that when the strange beige colour spreads throughout Alyx's body, it originates from her lower abdomen--where her uterus is. Plus, one of the Vortigaunts says, "There is a quickening!" The context would have us believe they are referring to her pulse, or to the fact that "quicken" means "stimulate" or "give or restore life to". But the word "quickening" also refers to when a fetus first begins to show signs of life, or begins to make movements that can be felt by the pregnant woman.

This is semi-foreshadowed by Eli's remarks that Alyx and Gordon would make a good couple, and that they can't "blame an old man for wanting grandkids." Additionally, it explains why the G-Man now takes such an interest in Alyx in particular: now that she's carrying his prime specimen's child, she's super-important to his schemes. That baby could play a vital role in some other intergalactic conflict of his, and it will be the price she pays for being saved from Black Mesa.

Chell will make an appearence in Half-Life Ep. 3.
It has been stated by Gabe Newell in an October 2007 interview that Chell has importance in the overall Half-Life universe, and will eventually have a fairly significant relationship with some of the other characters that we are already familiar with. Who knows, they are heading to the Borealis after all which is an Aperture ship, maybe a portal mishap leads Chell to Gordon's location or vice versa. Perhaps even G La DOS gets some Half Life time? I know most people think 'but Portal was set nearly 300 yrs after episode 2' but technically this was never confirmed so who knows. To this troper it appeared as though maybe 30 years at the most passed which would then put it into the HL continuaty. We may even see Chell with a speaking role but that's just wishful thinking. Gordon: ....
 * This is pretty much exactly my theory. But the Borealis drydock found inside Aperture, without the ship near it, probably doesn't have any teleportation qualities. Plus she's not at the drydock now anyway, having escaped. I always figured that if she ever ended up being teleported to the Borealis, the G-Man would have something to do with it. But if Gordon and company teleported into Aperture, there's the problem of "How do they get out, and then, how do they meet up with Chell, and how do they get back to Eastern Europe?" G-Man again? Then again, the Borealis could just be teleported outside of Aperture somewhere close to Chell's location.
 * I could just picture the romantic dialogue between Gordon and Chell as their relationship develops:

Chell: ....

The Cremators still exist in canon.
In Eli's lab, you can see a Cremator head in a jar, which Eli will tell you Alyx brought in, but they have no idea what it is. This means that the Cremator's head were built still, which means they're still in existence. Throughout the game, you happen upon burnt bodies in many places. Perhaps the Combine dispatch Cremators to destroy bodies, and they just aren't normally seen. Besides, they're a creepy enemy, and awesome looking. They deserve to exist.
 * At the risk of being meta, the Cremator's were probably a type of human-synth the Combine were designing but decided not to produce by the time their human forces were being finalised. A few prototypes were constructed however, but after the project was cancelled these were tossed and, the Combine treating the Earth as one big waste pit, their pieces ended up wherever. Alyx found the mask of one of them in one of her explorations and thought it was neat, showing her father, but Eli, being a scientist, decided to study it anyway. As for the bodies, Cremators were meant to vaporise corpses, so it probably isn't them.

Gordon sees the world as the player does
What this troper means is, is that in Half Life, Black Mesa is equal opportunity. Gordon was smart, but had several birth defects, including being LEGALLY blind. He could see, but barely. as an adult, he accepted a new technology from Black Mesa to regain a rudimentery form of sight. He sees the world with sub-par graphics eyes. After being in stasis, the G-man improved his eyesight, to the level of quality you see in Half life 2 and its episodes. in Episode 3, his eyes will see as well as whatever the graphics engine is (for us) in-game. why his sight was not returned to a normal humans' is not known though. Another idea i had is a tired one, but Gordon is dreaming in stasis as you play the game. he expierienced all that you saw, yes, but odds are the average human being, made of Steel or not, would still be afraid of Hunter fletchettes, exploding barrels and giant Synths. he was much more careful, due to the fact that HE is the one who feels the sting...and more. The last wmg i have is nearing Epileptic Trees, but everytime Gordon DOES die, the Gman transports him to an alternate universe with time going a few moments slower, i.e., Gordon "dies" or extremely close to it, and the Gman sends Gordon to one of the infinite universes there are, one, of course, being in the same setting, but minutes, hours, or days before. This process heals Gordon to his Pre-save health (Gman being the promotor of a "fair game"...mwahaha...). the only problem is that this tires Gman, and His Employers, whom aid this transition. so that explains the auto-saving. BTW, i am a new troper, hope i did'nt mess up the page.

The G-Man is the GM
Meaning game-master. The whole series is just a tabletop game where Gordon is the PC in a party of one. Explains G-Man's abilities, his habit of applying phlebontium wherever it's needed, his inability to interfere with events directly, and his protection of Gordon.
 * Best. Idea. EVER!

Episode 3 has been further delayed by the release of Portal 2
Because now they have to rewrite the whole game to include Rick the Adventure Sphere in an Atlas-style arm and leg chassis.

Episode 3 will have Left 4 Dead style co-op.
On the team will be Gordon, Alyx, Barney, Grigori, a Vortigaunt, and Adrian.
 * And Chell and Dog.

Areas in Portal 2 will be playable in the next HL game.
Everyone knows Gordon and teleportation don't mix. Once Gordon and company find the Borealis, they'll probably come across a teleporter of some sort, or maybe even the Portal gun. Once that happens, they'll probably end up traveling to the Borealis' drydock, which can be seen in Portal 2. This will be a Nostalgia Level, and they'll get out pretty quickly, but not before lots of Portal references.

Portal 2 and Episode Three are still connected, due to Time Travel
The Borealis vanished years ago, and suddenly reappeared in present day. It's known, at least by Eli and Kliener, to contain technology powerful enough to take the fight to the Combine, or destroy us all. This may actually be a method of Time Travel, which caused the Borealis to disappear and reappear. Also, the 'Slow Teleport' from Nova Prospekt to Kliener's lab may actually be Foreshadowing this. Put together with Portal 2's Time Skip, we can draw the conclusion that the two stories may still be connected, if only peripherally.
 * Some of GLaDOS's comments in the first Portal have led others to conclude that Portal occurs just before or during the Seven Hour War. While the "9999-" line could mean an overshoot, it is still possible that Portal 2 occurs during the Half-Life 2 arc (yes, Valve staff said the two Portals have hundreds of years between them, but they've changed their minds plenty of times before), allowing the possibility for the two plots to be related without involving Time Travel.

The government drugged the HECU Marines as part of an experiment
Before deployment, the HECU detachment had their food/water spiked with some kind of Psycho Serum that turned them into bloodthirsty killing machines. Think about it: not one of the marines ever seems to think it's strange that they're being sent en masse to mow down civilian scientists; they're completely unflinching, refusing to retreat, surrender, or even use cover, even when their squadmates are dropping like flies around them; they're nonsensically cruel, relishing the opportunity to mow down defenseless civilians; they possess single-minded dedication to killing Gordan, even though he's fended off hundreds of the soldiers; and they can't spell worth crap ("YORE DEAD FREEMAN"), due to the compound's degenerative effects on their minds. The marines that Shepherd runs into were not part of the HECU, and thus, were not subject to the experiment, explaining why they're not total psychos. Shepherd, knowing something was fishy, didn't take the pills/spiked rations/whatever; this ability to adapt is what made the G-Man curious.

All the people in City 17 probably thought Gordon Freeman was in another City, or in hiding.
Think about it; nobody asks what the hell happened to him over the past years, and everyone expects him to be a major Resistance fighter. See, only Breen knew that Gordon was in stasis when he made that announcement to Overwatch in Nova Prospekt.
 * This is canon. At the very most, Eli may have suspected the G-Man spirited Gordon off somewhere, but we don't know how much Eli knows about the G-Man beyond "he exists and is somehow involved in things." To borrow the way the timeline guide puts it: no one talks to Gordon about the past several years because the world changed so much that no one could have missed it, and they don't know technology exists (the G-Man's stasis/slow teleport) that would allow someone to miss it, so it would be like talking to a soldier in Afghanistan about 9/11; you don't see a need to discuss it.

The events of Portal 2 will CAUSE Episode 3.
This is why they've been so quiet about Episode 3 and stuff, is because it would spoil the ending for Portal 2!
 * Sorry man, but seeing as it has been confirmed that Portal 2 is taking place 200 years after the first game, any chance of our friend Chell screwing things up for the resistance are pretty null. Still, aperture science could probably still be involved in some fashion.
 * Untrue. Now that Portal 2 is out, it is painfully obvious that no more than a few decades have passed.
 * Word of God says that Chell will eventually have a "fairly significant relationship" with some characters we already know, so this could be at least partly true.

The Barnacle Tongues are not tongues...
They are their penises. Real life Barnacles have long penises (on scale, it would be like a human having a 50 foot penis). Who's to say alien ones don't?
 * Where are all the female barnacles? Also, such a long penis seems unnecessary, given that barnacles are always extremely close together or spread apart in separate rooms
 * Barncles (on Earth at least) don't have genders. They are all hermaphrodites. The barnacles could just be using those penis' to reproduce, just like they do in real life.

The Head-crabs are able to zombify humans because of The Green flu
The Head-crabs normally can only zombify creatures from there home world, but like ten or so years before The Black Mesa incident, While the events of left 4 dead 1 and 2 were going on, either Black Mesa, or Aperture Science figured out a cure that they sprayed into the atmosphere which made living creature a carrier, people rebuilt and the world was doing fine but when the incident happened it just happened to react to the head crabs biology making then be able to turn others into zombies. The combination of it and the head-crabs forcing changes meant to be on a vortigaunt made it so they changed the humans into those horrible creatures.
 * And so thats why the fast head-crab zombies scream sounds so much like a smoker to me.

Gordon spent some time as Special Forces before he went to college
He didn't know what to do with his life, signed up, made it into the SEALs or Green Berets or one of the other heavy-hitters in USSOCOM, got out, and did his BS on the GI Bill. That's why he can kick so much ass.
 * Seems reasonable, given that he spends a lot more time handing out whoop ass, instead of using that MIT Doctorate. Hell, he may even be a plant by the government, and not a scientist at all!

Black Mesa's firearm program was Team Fortress 2
Gordon spent a lot of time playing Team Fortress 2 explaining his reflexes amd use of firearms. and maybe it was in the form of a light gun arcade, thus explaining his handling of weapons. Black Mesa probably hosted the game during the their break times. Or even better it's the reason the Resonant Cascade happened in the first place. Someone probably hacked the server which lead to..Ahem.. unfortunate implications.
 * Well, that explains why I've always found the sniper rifle so goddamn useless.

Gordon Freeman is mute
Freeman is simply incapable of speaking. He uses sign language to communicate.
 * He must do it with robot hands coming from the HEV then, cause he never seems to let go of his gun/crowbar.
 * Alternatively, there is an LED screen on the front of the suit which displays what he is thinking at the time. The suit is telepathic.
 * The tipoff for this is during the intro of Half-Life - the announcer voice says, "Black Mesa is an equal opportunity employer."
 * Jossed by the game itself. Listen closely when you pick up ammo or a medkit. The HEV's suit is distinctly female, the other voice is distinctly male.

Dog actually works for the Combine
Dog's constant Deus Ex Machina appearances are far too convenient. He spends most of his time way off-screen (Unless he's interacting with Alyx), only to jump out of freakin' nowhere to pull some Big Damn Hero moment. For something that can tear apart a Strider with its bare hands, you'd think the resistance would give him a more frontline role. But no, Dog wanders off, contributes absolutely nothing to the cause, and only ever appears to save the day in a scripted event. For a character that actually doesn't do that much, he's awfully well-trusted by the good guys. Here's the facts: He's survived being cornered by the Combine at least twice (At BME, and shortly after leaving Kleiner's lab in the endgame of HL2), he's actively tried to kill Alyx and Gordon once (Episode 1. He just got un lucky with throwing the van), and his sole worthwhile contribution in Episode 2 was tearing apart the Strider outside White Mountain, and his appearance at that moment was conveniently timed. The clincher? He lets the Advisors kill Eli. He's supposed to be escorting everyone involved to the helicopter, but runs off for no discernible reason and only reappears in another BDH moment after Eli has been ganked. How damn convenient that possibly the only member of the resistance capable of putting the hurt on an Advisor just happened to stroll off just as the Advisors were planning to attack. Dog is a mole. He may not even be a willing mole (Given that a significant part of his body seems to be salvaged Combine tech), but his canny timing, inability to survive against the enemy off-screen, and suspect behaviour indicates that there's more to Dog than we're led to believe.
 * As much as this troper doesn't like this theory, there is some evidence for it- when the Resistance shuts off the superportal, Dog makes a noise that could be interpreted as dissapointment. The subtitles actually say "Dog Dissapointed", but it might be an automatic thing for one of his sound effects.
 * Dog is actually making the noise in response to Magnusson's exuberant celebration of his own genius - his headshake and the 'disappointed' sound effect line up with Magnusson's off-screen happy dance and Alyx's eyeroll.
 * This troper personally thinks Dog was a mole, but his attacking the Advisors at the end of Episode 2 was a permanent HeelFace Turn on his part.

The G-man works for Valve
The G-man is an agent sent by Valve after the creation of the Half-life universe to trigger the events necessary for the game's plot to occur. This also explains all the powers the G-man possesses, like stopping time at the end of Half-Life 2.

The HEV suit never was intended as a hazardous environment suit
Rather, it was a powered armour prototype disguised as one. It doesn't really protect you all that much from hazardous environments (though presumably the emissions in in the Anti-mass Spectrometer chamber were harmful, meaning that's one thing it DID work against), stops bullets better than it should, seems to give you the strength to use a crowbar as a weapon (they're unwieldy for that purpose) and has a freaking munitions counter. Its development was probably the result of the G-Man's involvement, as usual.
 * Isn't this Word of God? I mean, Adrian Shepard is issued an HEV suit at the beginning of his game, wouldn't make much sense to shove a Marine into a high-tech lab coat if it hadn't already had some combat capabilities. Oh, and the suit never had a helmet: how could it protect against hazardous gasses without a helmet?
 * Shepard had some kind of powered vest that luckily was compatible with HEV rechargers and batteries. As for the helmet, well, there's a flame war I don't expect to die down before the Heat Death. I personally am on the pro-helmet side, as he had a HUD, and headshots didn't turn his brain to chunky grey matter. One could say he had a force field and holographic projector, and that wouldn't be much of a stretch given what they had a Black Mesa, but why would you bother to do that if you could put a helmet on the damn thing instead? He just takes it off for publicity shots. Also, if Opposing Force were canonical, the helmet debate would be settled, as we see Gordon briefly, and he's not wearing one.
 * Not neccessarily, maybe the marines removed Gordon's helmet to properly identify him? Think about it, if you capture an enemy and their wearing a helmet, you'd take it off to report it to base/put a bullet in their brain/throw them in the trash compactor/whatever, don't you think?
 * Plus when you look at it all the dead guys in Xen had helmets, maybe gordo just had the good sense to quckily put an oxygen mask on after he entered the portal?
 * Shepard's armor was based on the HEV suit design, and was (IIRC) produced by Black Mesa. The main differences were reduced scientific instruments (unnecessary) and reduced armor coverage (increased mobility, decreased cost).
 * I've heard a theory that an armored hood and faceplate fold out from the back of the HEV suit. Hey, why not? Maybe in all the promotional pictures Gordon doesn't have it on because he prefers to feel the breeze on his face when he's not in combat, but when danger is imminent it folds back out. In any picture where he's in danger, he's just about to flip the hood on.
 * The thing's designed to be used in Xen. Of course it'll have some combat capabilities.

Eli hired Gordon from the G-Man.
The price for hiring someone from him though, is the death of a loved one because the hired one loses their free will until the contract is finished (basically, Gordon is a merc). However, after doing this, he then told the Vorts' to stop the G-Man when he tries to take his payment. The G-Man didn't mind, as he saw Gordon's usefulness to the Resistance and found the Combine annoying. After Alyx was on the ground, saved by the Vorts' the G-Man informed her of all of this. She is clearly angry, and the G-Man warns her Gordon has about 60 seconds of air left. She decides to get revenge and safe Gordon by making the deal of setting Gordon free (after the Combine are defeated) in trade for Eli, Mossman, and Barney's lives. Barney is killed off screen, Mossman is killed by the Combine, and Eli is killed by the Advisor. The ending was an act so people didn't catch on. The reason Eli was spooked by what the G-Man had Alyx tell him wasn't just because the G-Man had said that before at Black Mesa, but the G-Man visited him right after his deal with Alyx and said the same.
 * This would be interesting if it weren't completely ridiculous. Eli and Alyx have no reason to lie to Gordon (and it isn't as if he'll tell anyone), nor are they that good actors. The GMan doesn't negotiate, he tells other people what to do. It's redundant for anyone to hire Gordon as the GMan does that himself. And why would Alyx trade Barney's life when she barely knows him?
 * This idea still works if Eli's own life was the payment for Gordon's services, or if there was some other payment that we are as yet unaware of. Eli certainly knows of the G-Man's existence, and when Gordon first arrives in City 17, Barney and Dr. Kleiner don't seem like they're surprised that he's there in the first place, just that he showed up without any warning (Dr. Kleiner even says "I expected more warning", implying that he knew Gordon was coming, but he didn't know when.) In Episode 1, Alyx remarks on how Eli was "so sure [she] wouldn't find [Gordon]" still at the base of the Citadel. Perhaps the contract was merely for the destruction of the Citadel, and Eli figured that the G-Man would be taking Gordon back to wherever after that. However, the Vortigaunts, having gained a new admiration for Gordon upon seeing him in action during the uprising, decided to intervene and remove him from the G-Man's control so that he could continue to boost the morale of the Resistance.

The G-Man is Alex Mercer.
He arrives in places faster than you (Disguise + Running over obstacles), He speaks oddly (Ok, Alex doesn't speak weird, but all those voices would mesh sooner or later), He's super smart (arming a NUKE) and also is quite manipulative (Alex has absorbed some of the smartest people in Blackwatch, plus a lot of the people he consumed are Manipulative Bastards), and he's somewhat of an ass (like Alex).

Gordon Freeman was originally evil.
C'mon. A goatee? Seriously? He was just working at Black Mesa in order to build his doomsday gun, but the Resonance Cascade forced him to be a good guy by default. During HL2, he realized that being good could get ladies like Alex Vance to hang around with him voluntarily and has been reconsidering his ethics since then.
 * He became a good guy by slaughtering everything in his path. There's no reason he would have any changes to his ethics.

Black Mesa was built next to a certain landfill.
And somehow one of those E.T. cartridges made it into the anti-mass spectrometer. Nice job, Atari. You've caused a Resonance Cascade. After he's done killing endless waves of zombies, Gordon Freeman will sue the hell out of you.
 * This makes some sick sort of sense because half of Half Life is climbing out of holes, just like in that infuriating Atari game (which was the first game this Troper ever beat).

The Combine Will Arrive Right After The Infection.
Here's my theory on the timeline: Half Life - 200X, Left 4 Dead - 2009, Left 4 Dead 2 - 2009, 7 Hour War - 2012, Portal - 201X or 202X, Half Life 2 - 202X, E1 - 202X, E2 - 202X and E3 - 202X
 * Isn't it implied that the original game is taking place in the late 90's? Also, Portal is supposed to be taking place right around the same time as the Seven Hours War, not years later.

The Combine Assassin is still canon.
They have a training ground too. It's a building built by a company they stole those Energy Balls from. Yes, The Aperture Science Enrichment Center. Chell was a Rebel who somehow didn't get her mind wiped. That's why there aren't any by Half-Life 2. They were all dead and the Combine couldn't make more. GLaDOS was against them, but was forced to work for them. The employees gassed? Combine. The Morality Core? Combine Obedience Device. The attempt on Chell's life? A trick. She NEEDED to be killed to stop the creation of Assassins. This Was A Triumph (for the Rebels). Where is she singing from? A certain ship lost in the arctic. And, yes, there is Cake (ok, maybe no cake) and an Aperture Science Handheld Portal Device. The backup is activated on her death. She was given a plan by the G-Man. He saves Chell from mind-wipe, she gets her to activate the backup, and Gordon gets a Portal Gun. Perfect plan. Also, the HL2: E2 Combine Battle Network is based off of GLaDOS.

Gordon Freeman is no scientist.
The most technically advanced task he has undertaken is... wheeling a cart of dangerous radioactive materials into a reactor. While the real scientists watched from behind two layers of bulletproof glass. In Half-Life 2, he performed the likewise taxing task of plugging in Dr. Kleiner's teleportation machine. Gordon is in fact Black Mesa's janitor. Any references to his scientific credentials are only a cruel running joke among the Black Mesa staff. Whether he resents it or not cannot be determined until he brings himself to speak on the matter.
 * So basically, "You're not smart. You're not a scientist. You're not even a full-time employee!"
 * Gordon was in a bad economy. Having a PHD without any experience Gordon was (un)lucky his old professor (Kleiner) got him the Black Mesa janitor job.
 * A Ph.D. in theoretical physics is required for janitors at Black Mesa.
 * The mop is an application of the theoretical Kerr Metric magnetically coupled to a tungsten pole. The Hazard suit is neccesary to survive the radiation. The theoretical physicists insist that cleaning up messes in the rec room by removing the offending matter from reality may result in unforeseen consequences...
 * Well - it can be true. I heard about problems with servers which occured... after janitor was sarcastically told to power vacuum cleaner from UPS - which she did. Probably they want to avoid such problems and the payment rate adjusted with security clearance is similar.
 * This troper thinks Gordon Freeman, despite what Dr. Breen thinks, is a well-trained special military operative, perhaps placed within Black Mesa to watch over things.
 * Seeing as how Gordon's physics degree plays no part in any of the games as opposed to his skill in fieldcraft and asskickery, this seems entirely plausible. It's also possible Gordon is "a man of few words" because he doesn't want to blow his cover by saying something that would reveal his lack of scientific knowledge.
 * If he was placed in Black Mesa to watch the things it would probably be required for him to have knowledge about PHD 1) to not destroy cover 2) to know what is worth watching.
 * I have this theory that Gordon is actually a black ops trooper from Half Life who has amnesia and was reprogrammed by the Gman to be a scientist to infiltrate Black Mesa. Gman also gave him his PHD. Maybe this is why Gordon is so adept to firearms. Or he could have just spent alot of time in the hazard course.
 * It is still possible that he "barely" got the degree because of the propaganda war machine taking advantage of the fact that either due to illness or birth defect, he was mute. The reason why we never see him "talk" is because a) he can at least mouth the words, and the people that know him understand and b) his hands are always full and he cannot use sign language.
 * Well hey, maybe he got his degree AND combat training. Maybe in the near future, MIT has an ROTC program Gordon was in. His personnel file doesn't list his combat credentials because he wouldn't need those in a science lab. This is also why he does so much grunt work: The scientists see him as a Boisterous Bruiser because of his military background, and they don't want a knuckle dragger working on the important stuff. ...Um, hey, that's how ROTC works, right?
 * Hmm. Isn't american army financing the veterans (I'm not from USA so I only heard about this program)? In such case he might go to army only to have fundings of his PHD program.
 * Mostly Jossed. Considering that his thesis was called "Observation of Einstein-Podolsky-Rosen Entanglement on Supraquantum Structures by Induction Through Nonlinear Transuranic Crystal of Extremely Long Wavelength (ELW) Pulse from Mode-Locked Source Array", I think it's safe to say that he knows what he's doing.
 * Alternatively, Gordon Freeman is actually dying of some strange disease which does not allow him to speak. And his life-long dream was to become a famous theoretical physicist and save the world from an alien invasion, which is being granted by the Make-A-Wish foundation. It would certainly explain why everyone treats him like he's a genius for doing the simplest things.
 * More likely, that was some dying kid's wish and it is being granted to Gordon by Aperture Science's Take-A-Wish Foundation (Really, the TAW Foundation is canon and that is what it does). Destroying BM was just a side benefit.
 * Except the Take-A-Wish foundation was replaced by the Aperture Science Self-Esteem Fund for Girls, presumably because of the former's complete lack of good publicity. (According to Aperture Science.com's timeline, the US government made use of the Heimlich Counter-Maneuver to assassinate terrorists and the Portal program is obviously doing well. By process of elimination, the tier which was to be replaced is the TAW foundation. Heck, I think that Word of God even confirms this somewhere...)
 * The idea of it being a joke is evident with the G-Man. Whenever he addresses Freeman, it's either "Mister Freeman", or "Doctor Freeman" with a slight air of sarcasm on "doctor".
 * Not only that, in the first game everyone adresses him as Mr. Freeman, not Dr. Freeman. It's kind of condescending to do that to someone who's supposed to have earned a PhD.
 * Gordon does have those credentials... but so does everbody else. He's the new guy who does all the boring, dangerous stuff.
 * Also, the experiment had only just started. The work done by the other scientists consisted of checking that the sample was ready, giving Gordon instructions, and taking a few readings just before the resonance cascade. If there hadn't been a resonance cascade, they would have taken more readings, and subsequently analyzed them. This last part is where Gordon would have used his degree.
 * 27 is about right for a physicist who had just completed his education.
 * Perhaps he lost a bet and the beer store was closed.
 * Or it could be a dig at how the most challenging thing gamers do in games is... flip switches and plug in plugs.
 * While playing the games again, this troper couldn't help but notice that whenever someone addresses Gordon, they tend to talk a bit louder and slower, almost as if they're talking to a mentally retarded person. This is especially so when they are describing some task that needs to be done. Gordon's "PhD" may just be some fake certificate the Black Mesa scientists made to make him feel better.
 * There are many hints that Doctor Freeman is a really good scientisct on par with Eli Vance and Judith Mossman. The proof of this is that one of the first things we find out about Freeman upon his arival to Eli's hidout is that he got his place in Black Masa over Judith, who is shown to be a rather good scientis and a specialist in her field. Next, Eli Vance immediatelly states that he can't wait to get Gordon out of the HEV suit and into the labcoat, where he BELONGS. It is clear that Eli primarily saw Gordon as a scientist and a great aid in teleportation research.
 * Gordon Freeman is a postdoc. He's got the credentials, but he still needs refining under the tutelage of another scientist before he's really got his chops. Postdocs work long hours and do a lot of gruntwork in exchange for guided research and the chance to publish alongside a noted scientist (having a significant body of published work is the hallmark of a capable scientist at his prime. Publish or perish, as they say.) Gordon's thesis is directly related to teleportation; he likely applied for a postdoc position at both Aperture Science and Black Mesa. Black Mesa was the more prominent position (work for those crackpots at Aperture? Be a member of the laughingstock of the scientific community? Are you kidding?) plus the above-mentioned idea that Vance or Steiner was a former teacher/mentor and could help influence Black Mesa to hire him secured Gordon's choice to work for a quasi-governmental black operation.

Gordon's preternatural skills are due to more than the HEV suit.
Think about it; it explains so much. He wasn't the only guy with that suit--but only two other users even made it out of the facility, let alone accomplished the things Freeman has. The only explanation--other than that he's just that awesome--is that he has something nobody else has. Like, say... the ability to travel through time. No, seriously--your ability to save your game carries over into the game world. That explains how he never dies, how he always knows the proper way to beat a foe or solve a puzzle. It also explains why he sometimes does such mind-numblingly stupid things as climbing into a stalker pod; either he knew he could just reset to the moment before he climbed in if things went badly, or he knew it was the best available option because he'd already tried everything else! "vortigaunt: "Your bright face obscures your darker mask. [...] Far distant eyes look out through yours.[...] Could you but see the eyes inside your own, the minds in your mind.""
 * What's more, it's common knowledge among the resistance, as evidenced by lines like, "Don't worry, he's done this before." when Freeman "dies."
 * What if Gordon is actually the Prince of Persia?
 * In Portal, one of GLaDOS's taunts is "You wonder what happens after you die? I know." Possibly the afterlife in the Half Life universe involves other dimensions. When Gordon Freeman "dies", his "soul" is kept from leaving this dimension by the G-Man (or the Vortigaunts, when the time comes around), a new body is fabricated, they dig up a fresh HEV suit somewhere, and * pop* !
 * The ability to groundhog your way to inevitable success would be the most awesomest superpower, if it didn't come at a terrible cost. You see, because Gordon is an instrument of Fate, he can only ever do what Fate requires him to do. Any attempt to escape the road set ahead him and live happily ever after in some distant place not full of Combine, full of zombies, on fire, or full of Combine zombies on fire is brutally stymied by the dreaded Insurmountable Waist-Height Fence, Bottomless Pits, Deadly Water (or deadly waterfauna) or a cold, black screen informing Gordon that he has failed.
 * In fact, Gordon seems to be the sorting operator of a Many Worlds Stupid Sort Algorithm working on the premise "if (Gordon succeeds) continue; else destroyUniverse;", thus leaving only the universes where "the Freeman excels at all tasks" intact. Appearently, the Vortigaunts are aware of this, and calling Gordon "the one free man" is in fact a display of scathing irony on their part.
 * Or, due to his many universe nature, he is free, free to doom as many universes as he wants, kill resistence members with impunity, and choose about the gnome.
 * This Troper have always taken the gameworld in a very literal sense: Gordon's "powers" and his lack of freewill is simply due the fact he is controlled by a supravesal entity(a player, yes us) something that the G-man an the Vortigaunts is aware of. This is Lampshaded multiple time throughout the game.

"Freeman is in motion, fighting off a dozen Combine Elite with nothing but his crowbar. His speed is unimaginable--he seems able to predict his enemies' movements, even dodge bullets. The observer can't tell, but this battle is already over--Freeman has fought it over and over in infinite parallel existences, and he knows every possible outcome, as well as how to choose one that ends well for him. In countless other timelines, he's dead already--but he has a card up his sleeve that trumps all others: the F6 key."
 * Something I stumbled upon on DeviantArt:

The Crowbar is a powerful magical artifact, given by the G-man, and the source of Gordon's power

 * Gordon is completely powerless without it, even with the suit (see the first game), and then becomes an unstoppable killing machine after getting it.
 * It's originally found in a place where a crowbar would be unlikely, but the G-man has been seen.
 * In HL2, Barry gives it to Gordon saying "you dropped this back in Black Mesa" but at the end of the first game Gordon was in an alternate dimension, therefore the G-man must have given it to Barry.
 * Or crowbars are fairly common things that aren't that hard to find. I mean, each episode, they find a new one.
 * Actually it was probably due to the fact that at the end of Blue Shift, Barney teleports to various locations in Black Mesa and Xen, one of those locations is a room with a grate where you can see gordon being dragged off by HECU marines, his weapons have been confiscated and perhaps the crowbar that they confiscated from Gordon fell through the grate and got picked up by Barney, or it could be the crowbar Barney picks up after the elevator falls at the beginning of the invasion.
 * Immediately after the crowbar is disintegrated, the weapon scanner malfunctions and gives the gravity gun increased power and the ability to kill; this is a result of the power released from the crowbar destroying the thing that harmed it and then taking over the nearest suitable host.
 * Also, the gravity gun's transformation is remarkably similar to Gordon's...
 * Starts out: supposedly highly scientific, mainly used for physics puzzles, incapable of directly dealing damage
 * Ends up: indestructible, super-strong, killing machine

When the Resistance members remind Gordon to reload, they aren't referring to his gun.
They're reminding him to reload his saves often to do as well as possible on a given section. They want to live, after all.

Which meshes nicely with the idea that...

The G-Man is Gordon Freeman, from the future.
They have the same piercing green eyes, decisive nature, and a calm in the face of chaos and disaster around them. Obviously, at some point in the future, Gordon will gain a mastery over time and space (as well as corrective eye surgery to alleviate his need for glasses). He is now attempting to create a Stable Time Loop so that his past self will arrive in the same place he is now. As for why he seems to be angry and surprised at the interference of the Vortigaunts at the beginning of Episode One (since he presumably remembers it from the opposite perspective), well, he either tried and failed to change things, or he's just putting on an act to make them think he's lost control, and anyway, about a third of the way through Episode Two, thus potentially elevating him (in the case of the second possibility) to Magnificent Bastard status as well. Hell, some people compared pictures of Freeman and G-Man and found that their facial structure down to the bones is very, very similar.
 * Let's consider maybe he had his eye color changed, too. It'd be a rather subtle change, of course: Gordon has green eyes, G-Man as far as I've seen has blue eyes with just a touch of yellow around the pupils; from far away enough it's easy to mistake the two. Why, though, is currently beyond the scope of my powers of speculation.
 * Why? Discoloration due to aging.
 * This troper has thought the same thing (about the G-man being Gordon Freeman from the future), except that Gordon Freeman is mute because of a congenital malformation which will be surgically cured in the future. Gordon Freeman will learn to speak, but will always have a stilted quality to his speech.
 * Alternately, the reason Gordon never speaks is because he's embarrassed about his speech impediment.
 * Also, in Half-Life: Opposing Force, the G-Man tells Adrian Shepard that his ability to adapt and survive reminds the G-Man of himself. He does not tell this to Gordon Freeman, who has the same ability, because he doesn't need to. He is Gordon Freeman.
 * Why does the G-Man have a widow's peak, then?
 * Uh... A Wizard Did It?
 * Implants. Gordon Freeman has androgenic alopecia.
 * I'm no supporter of this theory, but I always thought if it's true, maybe Gordon has a widow's peak, but he really hates how he looks with one so he shaves it off. When he realizes he's the G-man he either just stops caring about it or starts to grow it out so he doesn't create a time paradox.
 * This Troper does support the theory. If you look at the Half-Life 2 covers with Gordon and the G-man, G-man's widow's peak is in the same place as Gordon's hairline. Ergo: G-Man gets a haircut to make it look like he has a widows peak, to make him look even creepier than he is.
 * That explains why the G-Man rescued Alyx from the Black Mesa. He knew he'd need her help in the future. Or... past. Or... his past and Gordon's future. Or... ARGH!
 * G man. That is all.

Gordon Freeman is the G-Man, from the future.
And he is trying to reverse what he had done in the past by posing as the puppet, but is really playing an extremely complex Gambit Roulette. The goatee, glasses and the muteness are all just for disguise.

Gordon Freeman is Gordon Freeman, from the future.
The events of "Half-Life 2" take place BEFORE the events of Half-Life 1, and at some point, he sends himself back in time to ensure that the events of the past cooincide with the events of the future, creating a stable time-loop.

Gordon Freeman from the future is Gordon Freeman
...Wait...

Gordon Freeman from the present is actually Iron Man
They both wear power armor.

Lamarr is Gordon Freeman, from the future.
Due to unforseen consequences of his actions throughout the series, he has turned into a head crab and is now trying to provide support to his past self [human Gordon Freeman] and the rest of the resistance.

The G-Man mimicks the facial features of whoever sees him.
The reason his face so closely resembles Gordon's (see - The G-Man is Gordon Freeman from the future) is because that's who the player is seeing him through. To a Vortigaunt, he'd look like one of them. To Alyx, he'd be a woman. It's possible that he has no true form of his own, or it could be that his true form is masked in this way.
 * Makes sense if he had a high-profile perception field, such as, I don't know... his TIE??? That's why he's always adjusting it!

The G-Man cannot sing in the key of 'G'.
Which is why he has such strange mannerisms when speaking, he is singing everything he says.

The G-Man is gay.
Stalking single men through the Black Mesa complex? Not stalking Barney, the one with a "Buy flowers for Linda" stickynote in his locker? Purplish tinge in his hair? Coincidence? I think not!

Gordon Freeman can breathe in space.
Gordon runs into various dead researchers in Xen, all of which are wearing powersuits with helmets, but he himself did not seem to need one. Gordon was used as a guinea pig for the same experiment that gave Batman the ability to breathe in space. It was not expected how this would affect the fate of the world in the Black Mesa Incident, however.
 * Possibly, the other dead researchers had helmets for protection, not because of low pressure or an airless environment. This might appear impossible, but Xen's anomalous gravity is at least as impossible as its apparently breathable atmosphere. The presence of Gordon's HEV suit HUD also seems to imply that he does have a helmet. He is seen without one several times in Opposing Force and Blue Shift, but these are non-canon.
 * This Troper conjectures that the HUD is projected onto his glasses by the HEV suit, Adrian's PCV is linked to his Gas Mask, and Barney's helmet has an eyepiece on it a la Halo Marines.
 * Adrian Shepherd managed to survive Xen's atmosphere just fine while wearing only a gas mask. Barney Calhoun did so wearing nothing but a security guard outfit. Incidentally, both games are canon, with Blue-Shift technically being more canon than Opposing Force.
 * Adrian Shepherd and Barney Calhoun can, obviously, both also breathe in space.
 * Word of God also states that Xen has an atmosphere and the previous visitors were just wearing helmets to avoid taking risks.
 * Not to mention that if Xen's atmosphere was dramatically different than Earth's, the aliens who lived there most likely wouldn't be able to survive very long here.

Alternative to the previous WMG, Gordon Freeman is Batman.
By this theory, Robin (not Batman's Robin) only corrected BATMAN'S not being able to breathe in space, and thus, Gordon Freeman is, in fact, Batman. This would contradict his not being a Scientist, and explain his preternatural skills. This theory is further evidenced when you consider that Batman Beyond turns Batman into a Legacy character, so Gordon could be a Batman between Bruce Wayne and Terry McGinnis - meaning Robin has in fact corrected this for every Batman.
 * Alternatively, Gordon Freeman is Bruce Wayne, possibly during one of his times leaving Gotham City (which have occured a few times during DC's plot). This explains how he's so handy with guns - Batman has been shown using them, both in his oldest eras and for ballistics study.
 * Sadly, there is a flaw with this theory. Gordon Freeman is quick to respond to enemy hostiles with lethal force. Batman has made an oath not to kill, so the two must be different people. While there is quite possibly a strong connection to the two, it is uncertain what that connection is.
 * Batman won't kill HUMANS (and even humans were fair game in early comics). He doesn't give a fuck about aliens and monsters.
 * Wait a minute, how's this for a connection: Gordon Freeman is partially Batman. The teleportation experiments, which have been shown to be able to (at least when breaking down) spontaneously retrieve things from alternate dimensions, once interrupted a battle between Batman and Mr. Freeze, in which Batman was being backed up by Commissioner Gordon, and what arrived in Black Mesa was an amalgam of Gordon, Freeze and Batman called Gordon...Free...man. He had Batman's combat and science skills, Gordon's appearance and Freeze's fancy HEV suit (and willingness to kill). Couldn't speak, though. They kept him around to monitor him, but he was so useful they made him up a fake identity and put him to work...okay, maybe this is getting out of hand.
 * Don't be silly, Gordon Freeman wears glasses! If he were Batman, how could he see?
 * The glasses are optical flats. They don't actually affect his vision. They're just the disguise.
 * Or, to make the disguise even better (Batman doesn't wear a bad disguise) the glasses are real, and he has to wear contact lenses underneath them. The contacts and glasses cancel each other out.
 * Of course, the price of doing that would be that his peripheral vision would suck, because he has distorted vision from the contacts that isn't being canceled by the glasses. Which, come to think of it, is true in the games. It's a First-Person Shooter, so you can only see the area directly in front of you, and not areas to the left and right that would ''normally' be visible. So now we have proof!

Alternative to the previous WMG, Gordon Freeman is that kid from Zathura.
Heck, if Batman could breathe in space, and the main characters in that movie could, why the heck not?

By the logic of the previous WMG, Gordon Freeman is Jimmy Neutron.
Think about it! He can breathe in space, he's (allegedly) a science genius, or course he's Jimmy Neutron!
 * Come to think of it, didn't Jimmy Neutron have a d&Atilde;˜g of sorts?

Gordon Freeman is actually Jason Todd.
This actually explains several of the issues here:
 * Being a former Robin, he would have all of Batman's skills; he also has no problem with killing (unlike Bruce Wayne).
 * Also due to being Robin, he could have had the same treatment to breathe in space.
 * Jason Todd's already come back from the dead once, so Freeman's ability to repeatedly resurrect himself may be an extension of this same ability.
 * Additionally, his death was caused by, so this would explain Freeman's affinity for crowbars.
 * Or, perhaps all of the Half-Life series is a Dying Dream being had by Jason Todd. Until he got better...

The G-Man is William Shatner in the future.
That explains the speech mannerisms. As for the G-Man's other powers, in the late 2100's Shatner will find a way to channel his awesomeness into energy, and use that to travel through time and space.

The G-Man worked for Aperture Science
Aperture Science and Black Mesa were competing with one another on a big government contract to develop working teleportation technology. Aperture knew that Black Mesa was getting close to a breakthrough, so they sent G-Man to infiltrate and deliver the Xen crystals to Dr. Vance in order to cause a chain reaction and ultimately destroy the facility. He then captures Freeman, hacks into GLaDOS and makes her kill all of the staff in Aperture Science to steal their secrets, including how to build a hand-held teleportation device that he builds into his briefcase!
 * Alternately, the G-man is actually Cave Johnson kept alive after his "death" through methods unknown.

The g-man's employers were the Vortigaunts
The Vortigaunts hired the g-man to bring about their freedom. He did this by providing the crystal sample for the test and causing an inter-dimensional war between Earth and Xen (the Black Mesa Incident). He originally intended to use Adrian Shephard to bring down the Nihilanth, but Gordon Freeman proved more resourceful and he manipulated events to bring about Gordon slaying Nihilanth. As payment for helping the Vortigaunts he obtained control of Xen ("for the time being") and was allowed to take Gordon Freeman as an employee.
 * An interesting idea. Possibly Jossed in the HL2 episodes, where it becomes apparent that the Vortigaunts are liberating Freeman from the G-Man, but perhaps by that time the G-Man had been rebelling against his former employers and trying to play events out for his own purposes.

Race X from Opposing Force are the Combine.
The G-Man sends Shepherd away because he's seen things he shouldn't. Incidentally, Shepherd's the only living person we know of who saw Race X, as the G-Man clearly doesn't care about people learning of the Borderworld inhabitants. Race X only shows up towards the end of the Black Mesa Incident, when the Nihilianth would have spent more time worrying about silly things like physicists with crowbars than maintaining the barrier between Xen and the Combine worlds. Once the barrier was weakened, the Combine dispatched a legion of Synths to bore through the Borderworld into Earth... and were promptly nuked. But they managed to find Earth and knew how to get to it through the Borderworld, thus setting up the events of the Seven Hour War.
 * This makes a surprising amount of sense (the Gene Worm especially could be a method the Combine use to harvest the resources of a planet), except for the part about the Synths, as none of the Race X have any mechanical additions whatsoever, which would preclude them from being any part of the Combine forces as all of them are shown to be "post-[insert species here]" of some sort. They could be a mercenary group the Combine use to investigate newly-discovered planets though, but that's stretching it a little.
 * It could possibly be that the Race X that Adrian saw was part of a Combine experiment in completely biological post-[species] creation. By extension, it was not a success (given that it was, as the OP said, promptly nuked), so the effort was scrapped and the Combine kept on relying on the 'old reliable' of mechanical augmentation, but the Combine still invaded Earth again when the opportunity came, just with the classical cyborg-and-overwhelming force combination this time.

Advisors are just Synths.
Well-made synths, naturally, capable of telepathy, but their feeble bodies makes them no more than advanced cell-phones... that can Mind Rape with their Naughty Tentacles. Note how at least a few of the Advisors we see are described as larval, seems odd to send a baby version of your master race to some alien world you plan on just strip-mining to death. Ergo, if there is a master race to the Combine, Advisors aren't it.
 * Hey, the Saiyans did it.
 * Space Pirates too.
 * In Dune, Feyd-Rautha and Glossu Rabban are both youthful administrative pawns of an older member of House Harkonnen, dispatched to oversee a planet valuable primarily for its mining resources. It's not an unheard-of tactic (saves effort on the part of the older members of the race who can attend to more pressing local matters, while still giving them the same level of control), and it makes a certain amount of sense, especially given the Advisors' telepathic abilities, that they would do so on Earth.

Alternately, the Advisers evolved from humans.
The Advisers were once just like us, but millenia of being waited on hand foot by their countless slaves have turned them into featureless sacks of fat who exist only to consume.
 * According to Raising The Bar, that's basically the intention when making them, but several things have changed in the episodes, so that could easily have been Retconned

Or maybe Advisors are just Combine middle management.
The fall of the Citadel and the death of Dr. Breen at the hands of the same man who originally took out the Nihilanth (a being of near-cosmic power, note) appears to have upgraded Earth's threat category from 'obscure resource world' to 'possible problem'. So several Combine Advisors (who we first saw as Dr. Breen's immediate supervisors) have now been sent in as crisis managers to handle the situation. Given the (implied) vast scope of the Combine, why should whoever their ruling powers are step in themselves, this early in the storyline? This is what lieutenants are for.
 * This could also explain why the Advisors were in the Citadel, as middle-management would be more effective on the planet than communicating from the Overworld.

Gordon could talk, once upon a time...
According to The Other Wiki, Gordon Freeman's doctoral thesis was titled Observation of Einstein-Podolsky-Rosen Entanglement on Supraquantum Structures by Induction Through Nonlinear Transuranic Crystal of Extremely Long Wavelength (ELW) Pulse from Mode-Locked Source Array. Clearly, he used up all his words for life in the title of this thesis. The body of text was completely blank. Apparently, the G-Man must have landed him the job at Black Mesa.
 * This troper notes that the thesis title is physics Jargon for "Shooting crystals with lasers to cause teleportation".
 * Which is exactly what he's doing in the first game.

Gordon could talk until the accident.
The radiation accident at the beginning of Half Life 1 permenantly fused his vocal cords. It is likely that his body was also turned to steel by the great magnetic field, thus his Made of Iron properties.
 * If not his entire body, at least his balls.
 * The Black Sabbath reference made me laugh, as did the completely random reference to Gordon's bollocks. Thank you, TV Tropes.

Gordon Freeman is Duke Nukem from the future
See above. He's got BALLS OF STEEEEEL.

The Combine and Aperture Science are related/Shared the same tech
First off, GLaDOS sounds remarkably similar to the Combine overwatch, especially in Episode 2. As well, the energy balls in the enrichment centre have more than a passing resemblance to the ones in the Combine citadel. The receptors are also very similar as seen in Episode One. As a final note, when Chell is hit by an energy ball, the portal gun disintrigrates the exact same way as the Combine soldiers guns when they are hit by an energy ball.
 * Though you're certainly right that Aperture seems to use a lot of technology formerly associated with the Combine before Portal's release, and you're right that the Overwatch and GLaDOS sound similar (because they are in fact both played by Ellen McLain) it's got to be noted that this technology is all used by the Combine Overwatch; that is, the human aspect of the Combine's presence. So, egg and chicken: It's possible Breen specifically equipped his transhuman forces with technology he ordered cannibalized from Aperture's Enrichment Center
 * Ellen McLain also voices The Announcer in Team Fortress 2. Maybe it's something GLaDOS does to pass the time while waiting for Gordon to show up on the Borealis. Her time with Chell is evidence enough that she has no problems watching people die, and many people believe that GLaDOS uses a backup of Chell's brain to send her through the test over and over again, much like the respawning aspect of Team Fortress 2.
 * I am going to go one further and say they are competing corporations. With this being the case, Chell is actually an Opposite Sex Clone of Freeman (with better eyesight), and they are extensively testing the clones in puzzles/non-linear thinking to have their OWN "Gordon" of sorts - they even staged the whole scenario with GLaDOS, with cost included, so that they would get the PERFECT Chell when she "escaped".

Lamarr holds the secret to defeating the Combine
Why else would Dr. Kleiner be so concerned about his pet headcrab? After all, there's no shortage of headcrabs about.
 * If so, launching him into the super-portal may have been a bad idea.
 * Unless that itself was the secret!
 * Just As Planned.
 * But the rocket was supposed to transmit to the Black Mesa anti-Portal Satellites, so s/he never had to deal with the superportal.
 * This troper argues that his concern is completely logical for a pet owner. After all, there's lots of dogs, cats, etc. around in the real world too.
 * This troper must point out that Dr. Kleiner put the cat into the teleporter to test it, and it didn't end happily. And that's a cute, cuddly cat. Rather than one of the most horrifying creatures you're ever likely to meet.
 * This troper must point out that Dr. Kleiner is more nuts than a room full of scrotums.
 * This troper believes that either Gordon or Alyx will die in Episode 3, followed by a "heart-to heart" from the G-Man saying how he took precautions to keep him/her alive, followed by one of the fuel tanks from the rocket crashing to Earth with Lamarr crawling out of it, zombifying the deceased party and fighting on your side/relinquishing control to you. Either that, or she zombifies the gnome into a vicious killing machine.
 * You'd be wrong; Lamarr was de-beaked and as such cannot turn people into zombies.
 * On the contrary, the death of whichever one or the crash would involve the top of the skull being ripped off. The beak, therefore, would no longer be necessary.
 * Or Lamarr could have gotten his/her beaks regenerated after returning from space.
 * Part of me hopes that Lamarr comes back as a Gonarch. Can you imagine having what is essentially a walking Multi Mook Melee in the body of an Antlion Guard, that shoots acid On your side?

The G-Man is a member of the Combine's master race...
He appears to be an uber-advanced alien, and the Combine (and Breen) seem to know who he is. He's just working freelance.
 * Building on this, wouldn't it make sense that the entire Combine Overworld wouldn't necessarily work together? G-Man is a powerful alien who decided (similar to Breen) to side with the winners.
 * Not neccessary - he might be renegate - like organizing ressistance on planets etc. He might want part of empire just for himself or do it from moral reasons or for entertainment (cmb can afford to lost one planet once in a while to celebrate some events)...
 * Further building, GMan is one of them taken to their fullest potential. While his brethren became reliant on their technology and slaves and removed their need for labour, GMan developed his abilities to the near-Reality Warper scale level of power he displays. Either bitter towards his brethren for squandering their gifts or simply ensuring no-one can ever equal or exceed his power, he begins to organise the destruction of the Combine.

The G-Man is a something of a third party contractor for interdimensional/multidimensional entities/Corporations/CosmicHorrors.
The way he acts and the way Breen talked about Gordon(i.e. the line about "your contract is open to the highest bidder") demonstrates that the G-Man may be mostly neutral in regards to earth. This troper views him as a sort of middle man. He is hired to enact a change, but direct action is not subtle enough to get the desired effect for his clients(whoever or whatever they may be), so he manipulates people close to the subject at hand to bring about the desired outcome. His job is to be a professional, pandimensional Magnificent Bastard. His clients took a fancy to Gordon, which is why the G-Man was told to keep him somewhere(I haven't played Half-Life in a long time but I swear the end of it contained a line about how his superiors wanted to use Gordon further.)

The G-Man and his employers have no interest in Barney Calhoun which is why(if memory serves me correctly, as it has been a few years since I played Blue Shift) there are almost no appearances of the G-Man in Blue Shift, or at least no of him observing Barney.

In Opposing Force, G-Man preserves Adrian in a similar method due to having a similar adaptability as Freeman, but he had to CONVINCE his superiors to keep him, after all by the end of Opposing Force they already had Freeman so why would they need him? The G-Man however recognizes talent for he line of work he needs done and likes having back ups.

== Gordon is The Painkiller. == "Faster than a bullet Terrifying scream Enraged and full of anger Hes half man and half machine"

Gordon kills people with weapons.

"Rides the metal monster Breathing smoke and fire Closing in with vengeance soaring high"

The "metal monster" is the dune buggy from HL2. It "breathes smoke and fire" with the gauss gun.

"He is the painkiller This is the painkiller"

Meaningless chorus

"Planets devastated Mankinds on its knees A saviour comes from out the skies In answer to their pleas

Through boiling clouds of thunder Blasting bolts of steel Evils going under deadly wheels"

After the 7-Hour War (devastates planets: check. mankind's on its knees: check.) Gordon comes out of stasis.

"He is the painkiller This is the painkiller"

Meaningless chorus

"Faster than a lazer bullet Louder than an atom bomb Chromium plated boiling metal Brighter than a thousand suns"

Gordon's able to overcome any threat, and typically borders on Refuge in Audacity with his entries.

"Flying high on rapture Stronger free and brave Nevermore encaptured Theyve been brought back from the grave"

Gordon eventually saves the human race from the Combine.

"With mankind ressurrected Forever to survive Returns from armageddon to the skies"

After the Half-Life series ends, Gordon goes back into stasis (or returns to the skies).

"He is the painkiller This is the painkiller Wings of steel painkiller Deadly wheels painkiller"

While he's in stasis after defeating the Combine, Gordon is idolized by the newly-saved human race as a saint, with wings of steel.

The G-Man is the Real Bad Guy
His manipulation of events might not be so much in Gordon's favor. Supported by the fact that the Vortiguants seem to have a negative reaction towards him.

Grand Unifying Theory on Gordon
Gordon is a mute genius. As such, he was hired by Black Mesa to prove that they are an "equal opportunity employer". However, since Gordon can't speak they wouldn't put him behind a desk announcing things, they'd put him out in the test chamber pressing buttons and observing things firsthand. Being made to push the cart wasn't an insult, it was the highest level position they could put him in that didn't require verbal communication with others. Barney's comments about pulling levers are references to this: Gordon's education didn't help him learn to speak and relegated him to the more menial tasks.

Gordon, while happy to have a job at an institution as large as Black Mesa, is still slightly pissed off at Breen and Dr. Magnusson for treating him like a stupid handicapped idiot, which explains the microwave casserole incident. Barney, however, got along fine with Gordon and the two of them were good friends and spent a lot of time together in airducts. Alyx's "man of few words" comment was because she didn't know he was mute, or alternatively just a joke at his expense.

The G-Man is just that; a literal G-Man
This troper thinks it would make sense that the government might have someone keeping watch over Black Mesa, and it was either his assignment or his own initiative to look after Gordon in turn; his seemingly mysterious ways could be explained by technology either developed by Black Mesa or Aperture Science, or possibly obtained through other means.
 * Inversely he is a gangsta or, as the phrase "G" originated from The Nation Of Gods & Earths, an Asiatic Black Man.
 * Where, curiously, in the Supreme Alphabet of The Nation of Gods and Earths, "G" stands for "God."

Myrmidonts fight to the death during spawning season.
You obtain the pheropod from the corpse of a Myrmidont; as demonstrated in the game, this works fine for attaining the allegiance of normal antlions, but other Myrmidonts will still attack you on sight.
 * However, it's possible that Myrmidonts are simply hostile to all humanoids (possibly with the intent of eating them, although you never get to see them doing anything except attacking people), given that they also kill Combine soldiers with no apparent provocation on their part.
 * All antlions seem to be relentlessly hostile towards anything living that doesn't smell like them (including humans without pheropods, the Combine and headcrab zombies, at least), but only the Myrmidonts also attack Gordon, who smells like a rival Myrmidont.

The G-Man was Barney
They both have the same voice actor. Gman isn't around whenever Gordon sees Barney. Gman doesn't pay attention to Barney, because HE KNOWS Barney (his past self) already makes it through alright. And when Valve does something horrible to Barney's character it just means he's turned into Gman.
 * During "A Red Letter Day" the GMan can be seen on one of the monitors while Barney is in the room. Still a good WMG, though.

Dr. Breen is related to Colonel Breen of Quatermass and the Pit
It may be possible to fit the Breen of Star Trek in there somewhere.
 * Or perhaps he's one of the Breens from Aeon Flux. He is actually a lot like Trevor Goodchild without the sex appeal.
 * WHHHYYYYYYYYYY?!

The Black Mesa Incident was an Evil Plan by Dr. Breen
Breen set up the entire incident, either because the Combine had already contacted him and promised to appoint him the head administrator of humanity, or because Evilutionary Biologist he believed the resulting struggle would strengthen mankind]].
 * It's obvious the Black Mesa Incident was that kind of plan. However this troper always thought the G-Man was it (and a very good one, indeed).
 * Seeing as Epsiode Two reveals that the g-man provided the crystal specimen for the original test, the above is pretty much confirmed.

Nihilanth was a Combine cyborg who rebelled & led his people to Xen to escape their tyranny.
That metal thing sticking out of him does look a lot like some of the other jagged metal stuff the Combine use, doesn't it? Also, the Grunts appear to be cyborgs as well, seeing as how they make a metallic noise when hit with the crowbar, even the apparently fleshy parts. The curious part is that even after they escape the Combine's slavery, the Nihilanth continues to use Vortigaunts as slaves. Chances are the Vortigaunts were slaves long before the Combine showed up. Maybe the irony was lost on Nihilanth.
 * As opposed to the hypothesis that Nihilanth IS a Combine cyborg, who leads his people in Xen under their tyranny? Free Vortigaunts captured by the combine are outfitted with the same green restraining gear they wore as slaves in the first game (look to your right when you get off of the train platform at the start of Half-Life 2). Important to note, Nihilanth sports a pair of gray manacles on all three of his wrists, just like the slaves do.
 * Wasn't it confirmed by the developers that the Nihilanth and Combine were old enemies and that the Nihilanth had to escape to Xen after its home dimension was conquered by the Combine?
 * Wasn't it also stated that the Vortigaunts were the Nihilianth's slaves and Freeman freed them? And don't forget how they're always prasing him for freeing them in the second game, despite having tried to murder him in the first.
 * Word of God, as vague as it continues to be, is that all the lifeforms encountered in Xen are not native, rather they were refugees from planets the Combine conquered that fled there to hide (inadvertently bringing some of their pest species with them as well). Aside from the common morphology indicating an evolutionary link between the Vortigaunts, the Controllers, the Grunts and the Nihilanth itself, the actual role of the Nihilanth before or after this exodus hasn't been stated, except that, yes, it used Vortigaunts as slave labour, so this WMG remains valid.

Gordon Freeman has a lisp.
As a result. He vehemently refuses to talk due to embarrassment.
 * Maybe we're just watching the recording of how he saved the universe and he went through and edited out all of his own dialogue.

Gordon Freeman is a vampire.
Regardless of graphical settings, he cannot be seen reflected in water or other surfaces. The HEV suit protects him from sunlight, although he may also be able to spend short periods of time exposed to the sun without protection, since he's forced to run along the rooftops to avoid the Combine, while wearing civilian attire, early in Half-Life 2.
 * It could also be because his HEV suit has some sort of active camouflage. Were there any reflective surfaces in the areas he walked in without the suit?
 * Gordon doesn't cast shadows, either. In fact, you never see your own character's shadow (or reflections) in a Source game (but you can see other peoples'). Thus, it gets a little weird if you extend this logic: All the terrorists and counter-terrorists from Counter-Strike are vampires!
 * This certainly explains why he wanted a job in the underground complex of Black Mesa, far from that pesky sun. Also, it's fun to imagine that maybe he was on fire for the whole rooftop chase in HL2, like a vampire in Buffyverse who's too plot-important to die from the sun.
 * That's why he nerver talks! To hide his fangs!

The G-Man is a mass hallucination.
But... Gordon is the only one who sees him.
 * Jossed in Episode 2, as a trigger word from the G-Man is used on Alyx, and Eli evidently talks about how he saw the G-Man back during Half-Life 1.

The G-Man is in the employ of a rival power to the Combine, working to destroy it.
He set up the Resonance Cascade to bring Xen into contact with Earth, leading to the Combine invasion. He knew that the Combine would conquer Earth, but there would be a human resistance. He unleashed Gordon at the right time to trigger a full-scale revolt capable of toppling the Combine on Earth. He also knows that humans will not settle for their own liberation - they will not rest until the entire Combine Empire lies in ruins. While he had other plans for Gordon after the destruction of the Citadel, things are still going mostly according to plan.
 * Alyx Vance serves a number of roles. For one, she provided motivation in the early days of the Resistance, especially for Eli Vance. She herself is a badass, and if Gordon dies, the G-Man will promptly recruit Alyx as his primary weapon. Finally, you can bet that Gordon and Alyx's children figure into the destruction of the Combine.
 * Which fits in nicely with the Portal WMG theory which states that the G-Man is their magical time travelling baby.
 * Furthermore, Judith Mossman is also working for the G-Man. She kept Breen from crushing the Resistance, kept the Resistance from revolting prematurely, and even kept Alyx in the field so she could gain necessary combat skills. Her mission to the Borealis was under direct order from the G-Man.
 * Also I reckon that, after Gordon's work for the Vorts in Ep1 (against G-Man's wishes), the G-Man's superiors have improved their opinion of Gordon, and instructed the G-Man to see if Gordon would be interested in some kind of apprenticeship towards becoming a G-Man himself. This, I think, is the reason for G-Man's "heart-to-heart" with Gordon in Ep2, and why he allows Gordon to see him implanting the memory into Alyx - essentially, he's giving him a bit of early work experience.
 * Even Eli's death may be part of his plan - it will ensure the extinction of the Advisors at the hands of an enraged Gordon and Alyx.

The G-Man is Nyarlathotep
Sure, Nyarly's human avatar usually has dark skin, but changing one's skin colour shouldn't be a problem for the god with a thousand forms. G-Man is clearly not a human, posessing strange powers and knowing things that normal peopel shouldn't. Also, Nyarly does have a habit of appearing as a figure of authority (such as a business man, a scientist or a goverment employee). If he would indeed be an avatar of an alien god, it would explain a lot of his abilities. He has clearly orchestrated that Black Mesa incident and the coming of Combine to further his schemes of awaking the Great Old Ones, which will end in the destruction of both mankind and Combine.
 * So, Barney might wind up killing Azathoth? Awesome.
 * Why is this the first time that anyone has connected Half Life with the Cthulhu Mythos?
 * This troper would like to know too. Particularly since the first thing she thought upon encountering the G-Man was, "You're Nyarlathotep, aren't you? AREN'T YOU?!"

Alyx Vance is completely and totally in love with Gordon.
For a start, she probably grew up hearing about him from her father - the young scientist who almost single-handedly saved the day. She builds up this image of Gordon as this superhuman figure. Then she rescues Gordon, and she sees that he isn't invincible. But then he puts on the hazard suit, and he's just as powerful as he was in the stories Eli told her. That is the clincher. She completely falls for him.
 * Ah, who can blame her...
 * Not to mention the evidence - Alyx herself does a convincing portrayal of someone who's just met her knight in shining hazardous environment suit, and even Barney comments on the apparent chemistry between Alyx and Gordon.
 * She tells him "Be careful" when he's about to go up against Breen. You only say that if you're truly concerned about the person in question getting hurt - if you would rather they fail but live than succeed at the cost of their life.
 * Something else of note-Episode 1 ends with the Citadel exploding, and Gordon blacking out. Episode 2 begins with the only cutscene in the Half-Life franchise-almost certainly representing what Gordon is thinking about during the explosion. So what is in the cutscene? Alyx helping Gordon infiltrating the Citadel, Alyx killing zombies in the hospital, Alyx suffering an attack from an Advisor etc. Looks like our favorite Heroic Mime can still return Alyx's affection.
 * Also Eli seems to indicate it (while Alyx says they are Just Friends he says that "[she] can't blame old man for wanting grandchildren".

The G-Man prevents Gordon from talking.
Theorize what you will about Half-Life, but from 2 onward, the G-Man prevents Gordon from speaking so that his knowledge of how the G-Man operates doesn't ruin the plot for the player. Or maybe just 'cause it makes the G-man chuckle whenever Gordon knows the obvious solution to a problem and he can't tell Alyx/Barney/the player.

Eli Vance will be back, but as an Advisor
Think about it, the Combine could easily use the genius of Eli Vance to create new technologies as an Advisor, instead of merely killing him. Also, host bodies were offered to Dr. Breen and seem to be able to be provided by current Advisors.
 * Valve would earn this troper's eternal hatred if they made us kill an Advisor with Eli's mind in the next Half-Life.
 * That's an awesome idea.

Poison Zombies are pissed that they have to carry so many headcrabs.
Think about it. You've got three or four of these things on your back, and they're heavy enough to make you walk hunched over. Then you see some cocky bastard who's carrying around nothing but a crowbar. It's only natural that you'd try to get him to pull his own weight.
 * All normal zombies just want someone (Gordon) to help get the headcrab off their head (listen to their cries reversed), but when they get close enough to him, the headcrab takes over and makes the zombie attack.

One day, Gordon will invent an isotop so volatile that it does not have a half-life but quarter-life
They will have to observe with hasty. This troper is a huge physics nerd and joked with fellow nerds that since (1/2)^2 =1/4, half-life 2 (written by valve as half-life^2 ) should have been named quarter-life
 * He will then use this isotop to defeat the enemies.

G-Man works for the Cosmic Maintenance company
Moorcock, Heinlein & Lequare, Ltd is the multiversal contractor of universe maintenance. When a universe under goes technical difficulties, a Cosmic Maintenance Man is often dispatched to sort the continuitium out. Although this may take time, as there are only a finite number of Cosmic Maintenance Men and an infinite number of universes, if Hugh Everett is right, anyways.

To help with the ever increasing workload, G-Man has been assigned with the task of harnessing the resource that is Gordon Freeman. The typical Hero With A Thousand Faces is a power that, until now, MH&L, Ltd had not yet been able to control, but G-Man offered a interesting solution to the usual refusal of voluntary services that most Heroic Mimes answer with. Mainly, this is done through liberal helpings of Mind Screw.

The events of Halflife are being manipulated by the G-Man in order to produce a One-Man Army that can adapt to situations in a heartbeat, be accustom to sudden upgrades in order to complete a suddenly difficult mission and generally be immune to the effects of being dumped randomly in hazardous situations and being left there until the right man in the wrong place can sort things out, defeat the bad guys and get the universe going in the direction that MH&L, Ltd feel is most appropriate for the universe.

Once Freeman is fully trained, there's already a universe selected that he needs to fix. And then G-Man has some other individuals scouted out for the next recruitments.

Gordon Freeman uses the same crowbar in all the Half Life games and Episodes
Because... why not?
 * It sort of got disintegrated that one time.
 * It got better.
 * Barney was inside the Citadel at the time in Civil Protection disguise and managed to get it once it teleported into the confiscation room. Then, after the train crash, it flew through a tunnel, around the corner, then into some gears.
 * Except that, when he gives you the crowbar in Episode One, Barney specifically says that he has a limited supply of crowbars "so try not to lose this one, okay?"
 * Polycount aside, the HL1 crowbar seems have a different shape than the HL2 one, if the HUD graphics are anything to go by.

Civilians in City-17 are extremely resistant to pain.
Evidence: when you set a civilian on fire, they walk around for a bit, then die. When you set a CP or Combine soldier on fire, they thrash around in agony, then die.
 * Must be the water.
 * Apathy and depression can do wonderful things for pain tolerance.

Alyx looks better in the Episodes One and Two because the Suppression Field is down.
Alyx Vance's slightly upgraded look in the episodes isn't just because of improvements in graphics since Half Life 2, but because the Combine Suppression Field that canceled reproductive desires has been destroyed, literally making her look more attractive to Gordon.
 * Except that all the suppression field did was prevent proteins from forming in the uterus. It was pretty much just like a mass birth-control machine.
 * Thatâ€™s what the Combine wants you to think!
 * Seeing as Breen's whole suppression field speech revolves around "instict" I imagine the device also somehow chemicaly castrates the populace. Stopping certain proteins from forming in the brain perhaps?
 * If they could do that, couldn't the combine just mind control the entire human race to ENJOY the oppressive situation they are in?

The Borealis contains a Time Machine
Aperture Science has been shown to have created technology several times more advanced then the rest of the Half-Life universe. (For example, both GLaDOS and the ASHPD are more advanced then the HL2's closest examples, D0g and Kliener's teleporter.) The Borealis originally disappeared when Chell activated the time machine to protect it from the Combine. (Which would take place in Portal 2, making Portal set between Half-Life and Half-Life 2).
 * Does that mean the last scene of Episode Three will be a fade to black with a door of light opening and you just hear "Come with me" as The Doctor finally arrives on the scene?

The G-Man is just an alien suitcase.
And he's controlling a corpse. Think about it. He's very pale, isn't comfortable with speech and so very obviously isn't human, yet he looks like one. He seemed to have less power when he was stopped by vortugaunts, the only time he didn't have a suitcase.
 * Explains why he was so reluctant to talk about a briefcase injury in Concerned, and why he's so hard to kill without insane amounts of explosives.

The G-Man is God.
Think about it. He can teleport, stop time, control other beings, transfer objects anywhere in the space-time continuum, steal things from other universes, can't be damaged by any weapons ever unless you're abusing Garry's Mod, can't even be hindered except by the Vorts, and the entire race has to hold the barrier against him at the same time (seriously, if even four of them stop focusing on it, it falls), and oh yeah, is named the G-man. You know, the god-man?
 * To connect this with the "Gordon Freeman is the G-Man" theory, the G-Man/God became mortal for some inscrutable purpose which we mere mortals cannot hope to fathom (that is to say, for kicks), and while in this state is known as Gordon Freeman. Either He's spent a long time as Gordon Freeman (maybe He takes a brief vacation every few years) or He's rewritten everybody's memories to make them think He's been there for longer than He has. The G-Man/God is able to appear because He is omnipresent/beyond time. It's very likely that, in order to enjoy his vacation time, He's also rewritten HIS memories, so that He really thinks that He's Gordon Freeman. But He also watches over Himself from other points in time, and once His vacation is over, the G-Man/God restores him to his previous state. This is also why he's so hard to kill, and has a mastery of almost every single skill needed. He's GOD, after all. He just doesn't know it.
 * To add to this, he actually rewrites the entire history and nature of the world before "descending," so that his vacation will be rather more interesting. Then, once he's done, he sets everything back to the way it was before.
 * On a more sane role for Freeman under the theroy, he is like Joshua, and god is helping him to defeat his enemys.

Poison zombies are bloated because they are full of eggs
Poison headcrabs reproduce by taking a host and then having a massive orgy on its back and filling it full of eggs. These hatch and the zombie is eatten by baby headcrabs from the inside out.
 * Oh my goodness.

Adrian Shepherd will be sent to retrieve Freeman by the G-Man
For whatever reason, the G-Man can't just blip Gordon back out. He still has Shepherd in storage. Humans can take action without restriction, and the G-Man can implant orders into people. This will end violently.
 * But why? Without Vance, Gordon is the Resistance's only hope. The only plausible use for Shepherd is to provide back-up during the combat operations the Resistance will encounter. After all, the guy is a Marine.
 * The G-Man isn't on the side of the Resistance. The Resistance's contract for Gordon ended with the destruction of the Citadel. Adrian would be used as the G-Man's Repo Man, not as Gordon's backup.
 * This theory's been scrapped, it seems that the G-Man really didn't seem to mind not having control of Freeman during Episode One.
 * Insert obligatory "That's what he wants you to think".

There is a scenario similar to Chzo Mythos, and Gordon Freeman is actually not Gordon Freeman.
Just like in 7 Days a Stranger, Gordon might be someone else who everybody mistakes for Gordon, who has possibly killed the real Gordon for some reason. That's why he doesn't talk: To not betray his ignorance about particle physics.
 * Odd his college professor and his best buddy for years recognize him if that's the case.

Gordon's mouth is full.
His suit doesn't have enough pockets, so he's forced to carry a few guns in his mouth. That's why he doesn't talk.

The G-Man was pulling Alyx out of the Citadel with Gordon
We know that he saved her once before, and that he considered her a valued investment. Whether he was going to keep her with Gordon, or deliver her to Eli is yet unknown. What Eli did to get the G-Man to rescue her from Black Mesa will be important in the future.
 * He didn't start including Alyx in his plans until Episode Two. Until then, she was cannon fodder. He's including her as something more than fodder because the Vortigaunts (the only beings capable of rejecting his plans) consider her important.
 * He states during the extended auto-fellation scene carried out while the Vortigaunts are saving Alyx that he was the only one among his cohorts who saw the wisdom of saving her during the original Black Mesa incident, and boy-howdy, turns out he was the genius after all.

Alyx is wearing Unobtainium.
Alyx is Made of Iron for no apparent reason. Maybe she has some advanced combat technology that was developed by her father and Dr. Kleiner to fight the Combine. The same may also apply to other resistance members.
 * Her clothes are quite obviously patched with duct tape. The question is why they haven't thought to slap a layer of that on the HEV suit.

GLaDOS' backup is on the Borealis, where she and Freeman shall have some cake.
Also, whilst he is smart and a scientist, he is also a full-time employee - of Black Mesa. Turrets ensue.
 * And, based on a theory that GLaDOS has Chell backed up on file, Freeman will storm the Combine with an army of Chell clones.

Half-Life doesn't take place on Earth, but on a world in Warhammer 40000.
Think about it. The reason teleportation is so dangerous is because it involves passing through the Warp. Xen is a daemon world in the Eye of Terror, and the Nihilanth and its allies are followers of Tzeentch. The ant lions are a stranded strain of Tyranid that lost their connection with the Hive Mind until they rebuilt sufficient strength, and so are the headcrabs. The Combine are a special-operations force from the Tau Empire. The G-Man is either the Deceiver or an Eldar Farseer. The HEV suit was reverse-engineered from power armour.
 * In that case, Gordon is a Primarch. It explains his awesomeness quite well, no?
 * Most certainly-the Emperor himself was a brilliant scientist and quite a badass, so like father, like son...
 * And so all references to things such as Earth, or (insert Earth location) are simply due to the original colonists' habit of naming things after places on Earth. Do we ever see a map of the world?
 * Actually, yes, you do see a map on a computer screen near the garage at the end of Episode 2, and it is indeed of Earth. Also, there's a circle around eastern Europe, and more specifically the Ukraine, witch must mean that the game takes place in or near the Ukraine.

After Eli Vance dies, his brain will be put into d0g's body, or another robot body.
Eli built d0g not only to protect Alyx, but as a last-ditch effort to becoming immortal. His prosthetic leg is the first step (no pun intended) in his trans-humanization efforts.
 * Uh, no. Word of god states that he lost his leg to a bullsquid.

The cassarole incident with Magnusson? Not an accident.
Gordon Freeman's deepest desire is to recognized for his scientific intelligence. Freeman also hates Magnusson, since Freeman is stuck carting around isotopes and the one who gets recognized is a jerk like Magnusson. So Freeman saw Magnusson's beloved cassarole and took an oppurtunity...

The Crowbar is forged from the one ring.
Think about it. The crowbar looks always the same, if you hold it to a fire, Gordon doesn't get his hands burned and most important: It always returns to its master. So, Gordon is also Sauron, the Dark Lord!
 * "My precious crowbar... me wants it!"

The Xenians were protecting Earth from the Combine.
When the creatures from Xen first invaded, it was because they were trying to stop the human scientists from messing around with portal technology, since the Combine could detect such incursions. When Nihlanth was destroyed, now nothing stood in the way of the Combine, who promptly invaded. Need I say it?
 * Word of God is that the Xen army had their backs to the wall. Nihlanth was out of options and desperate. When a portal opened to Earth, a world that was free of Combine, he took the first chance he got and ran like hell, figuring nothing could be worse than the Combine. It failed, and his death caused the portals to remain open.

Gordon Freeman is a crazed psychopath who enjoys murdering innocent scientists.
Come on, who of us hasn't used cheats to give Gordon a gun before the Resonance Cascade and kill your fellow scientists? Some of us even continue working through the whole game, offing the people we are trying to rescue after they've served their useful purpose (i.e. opening a door). "Scientist: Ah! Hello, Gordon Freeman! It's good to see-- (BLAM!)"

Gordon Freeman is Black Sabbath's "Iron Man".
Freeman's durability would be explained by being "turned to steel". He can't get over waist high fences due to the "boots of lead".

The Vortigaunts are evolving.
As evidenced by their elevation from weak mooks in Half Life to Badass killing machines in Episode Two. Also, note the change in skin texture and vocal outputs. This has something to do with the growing power of the Vortessence.
 * I'm not sure how much of the change in the appearance of the Vortiguants is due to changes in graphics as opposed to in-universe events, but their seemingly more impressive combat abilities are probably a combination of fighting someone other than a one man army, and no longer being under the control of an oppressive overlord. The Nihalanth didn't seem like the type to let a slave race develope its abilities to the fullest.
 * Correction, they have held off one swarm of Antlions and the G-man. They fail when facing anybody who brought a gun.
 * Unless the person with the gun is an HECU marine. Remember that they were part of the Xen force that tried to conquer earth.
 * They were being used as expendable cannon fodder at the time. The alien Grunts were the members of Nihalanth's forces that were doing the heavy lifting.
 * Plus if you look in Half Life they are wearing similar colars to those that the combine would go on to make them wear
 * Hmm. I guess that collar surpresses their conection with the Force Vortessence and therfore the Jedi Vortigaunts does not fight so efectivly.

The Combine can not control the Vortiguants.
The only living Vortiguants you see in Half Life 2 and later are in the company of the Resistance. Despite having a number of abilities that would make them more useful as a slave race than humans, you only ever see them tortured to death in Nova Prospekt. And comments from Episode Two would indicate that they are an actual physical threat to the Advisors. Humans could be threatened with pain and death, and altered with surgery. Vortiguants, however, did not fall to such things.
 * You have a point. There is an enslaved Vortigaunt, HL1 bracelets and all, in the station at the beginning of HL2. Why not a Vortigaunt Synth? Why no Vortigaunt Zombies?
 * Except that you do see one enslaved Vortigaunt right at the start of Half Life 2, cleaning floors in the train station, behind a fence.
 * He could have been biding his time, waiting for the One Free Man to arrive as a cue to throw down his oppressive collar. If the collar is the same as the ones Nihalanth used, the Combine probably don't really know how it works.

We have never seen a true Headcrab Zombie
Headcrabs are probably native to the Vortigaunt homeworld. They evolved zombie powers to deal with Vortigaunts and their electric attacks. When one possesses a human, though, they do not know the difference and force the mutation they'd normally execute on a Vortigaunt.
 * Which is why they can't walk properly when controlling a human.

The HECU is not a Marine operation. It is, instead, Bad Company.
This troper has a quite a few family in the Corps, and when presented with even a fraction of the evidence, they scream and moan that the HECU is, in fact, not Marine. Added to the behavior of the unit in a clear combat zone, they resemble more of a motley crew of ragtags and misfits from the Army than Special Forces Marines. Hence, the HECU is not Marine, but is, in fact, Bad Company, sent to clear the way for the Black-Ops, then be silenced themselves.
 * That... makes tons of sense. It also explains why their equipment sucks so much (sub machine guns as opposed to assault rifles, M1 Abrams that can be destroyed by rockets when real ones require simply ridiculous amounts of explosives to destroy, world war 2 era grenades, etc.)

Gordon Freeman is Max Payne
After the horrific events of the first two Payne games, the governemnt used Max's college minor and some intense training to put him in an out of the way facillity studying some pointless energy crap. And changed his name. Of course, that all went to hell. The HEV suit simply dumps loads of painkillers into the hero's body when he is injured. And the film/noir secret behind this move? They stole Max/Gordon's bullet-time. And gave it to the G-Man. That's why the government has been interested in Max all this time. They wanted his bullet-time.

Alyx Vance died during the Black Mesa incident, the â€œAlyxâ€� we know and love is Eliâ€™s replacement
Eli Vanceâ€™s daughter Alyx died with her mother in Black Mesa, killed by a Bullsquid. Eli eventually took in one of the many orphans left by the Seven Hour War (one who remained Eli of his deceased daughter) and raised her as his late daughter Alyx. While Eli came to genuinely to care for his adopted daughter he could never bring himself to tell â€œAlyxâ€� the truth. Eli Vanceâ€™s daughter Alyx died with her mother in Black Mesa, but Eli Vance built an advanced android to replace his daughter. It was stated or implied in episode 2 that the G-man rescued Alyx from Black Mesa, and he further implies it was only because he plans to use her.
 * Eli eventually did love â€œAlyxâ€� as a daughter, for who she was and not who she was supposed to replace.
 * Which explains a previous theory regarding Alyxâ€™s Made of Iron tendencies. Alyx isnâ€™t wearing Unobtainium, she is made of Unobtainium.
 * It could be possible that the G-Man was lying about his true purposes for saving Alyx. Eli may have made a proverbial deal with the devil with the G-Man, having the G-Man save his daughter from certain death in exchange for... something. When Eli was unable to perform that favor, the G-Man allowed Eli to die. Or maybe the original deal was to have Eli die at a later date, just so the G-Man can watch her cry, because that's how he rolls.

Gordon Freeman is a headcrab zombie
Even as a headcrab zombie Gordon still fights for both humanity & Earth, suppressing his desire to kill and channeling his murderous intent against the Combine. In the initial resonance cascade Gordon was briefly teleported to Xen. Alone, disoriented, unarmed, and without a helmet Gordon was easy prey for headcrabs. Soon after zombification Gordon had the strength of will to remove the headcrab but still survive as a zombie. Gordon remains silent as not to betray his true nature, if he talked everyone would know. Would the resistance still follow Gordon if they knew the truth? Would Barney, Eli, and Kleiner put their trust in a headcrab Zombie? Alyx, what would Alyx do if she knew the monster Gordon has become? All questions Gordon doesn't want answered. When humanity is free and our world restored Gordon will turn his crowbar on the world's last threat. . . himself.
 * While I seriously doubt this will actually happen, it would be the most awesome ending imaginable for the series. True Art Is Angsty!
 * Alternately, he's still got that headcrab up there, and everyone's just politely ignoring it as they would a pimple or a bit of spinach caught in his teeth.

Valve is the Combine
Valve's games are their more subtle version of the reproductive suppression field - they keep countless potential Badass Bookworms like Gordon Freeman from reproducing, since they're too busy playing Valve games and writing about those games on this website.
 * That would mean TV Tropes is an adjunct of the Combine, even if an unknowing one.
 * Then it's raping time! Make babys with much hasty!
 * Actually, think about it. They're preventing us from fighting them by giving us a training simulator. Doesn't that just create MORE Gordon Freemans?

Due to a Vortigaunt prophecy, Gordon Freeman is the only person who can kill the G-Man.
As a result, Freeman has been made a major factor in the G-Man's plans. In the first game, he engineered the Black Mesa Incident in order to kill Freeman. When Freeman survived, the G-Man decided "if you can't beat 'em, join 'em" and forced Gordon into working for him. When the Vortigaunts freed Gordon, the G-man began working desperately not only to get things back under his control, but to prove to his usperiors, the Vortigaunts and himself that his destiny is his own and it is most certainly not to die at the hands of a not-scientist because a bunch of magical aliens with throat problems said so.
 * Also, "prepare for unforseen consequences" is his way of saying Screw Destiny.

In the absence of Gordon, Alyx is now the G-Man's agent.
Gordon is apparently no longer under the G-Man's control. To keep the war in his favor, the G-Man recruited the next best person: Alyx Vance, who works closely with Gordon and is a major player in the war. To keep the Vorigaunts off his trail, the G-Man made his control over Alyx much more covert, implanting several Manchurian Agent-style triggers in her. The one Gordon saw in Episode 2 "Prepare for unforseen consequences," is just one of many commands the G-Man has given to Alyx.

The G-Man is the Starscream.
In the first game, he mentioned his superiors. In the second and onwards, he speaks as if he was the one in charge. The answer is simple: he had superiors in the first game, but decided he could do a better job then they could and had them killed.
 * This troper came to the same conclusion.
 * Alternatively, his superiors were the Combine. The first game has him engineer the Resonance Cascade, providing the Combine with access to a new world, as well as removing a strong force that did and continued to resist their rule. Naturally, the Combine turn on the GMan the moment he has outlived his usefulness, and that makes him very angry (very angry indeed).

The Resonance Cascade gave Gordon superpowers.
Think about it. Prior to the Resonance Cascade, Gordon did nothing extraordinary. Afterwards, he's a One-Man Army. Maybe some Xen lifeform merged with Gordon, not altering his mind or appearance, but making him nigh-invincible.
 * Perhaps this lifeform also removed his ability to speak?
 * Console mode is an extension of this: Gordon's nascent telekinetic abilities allow him to erect an impervious personal shield (God Mode); increase the power of his superior kinetic weapons (weapon damage increase); allow for staggering feats of jumping, nay even flying, and passing through walls (gravity, no clip) and at the highest levels achieving complete mastery of the time-space continuum, making things appear from thin air and teleporting himself anywhere (give "item", make "enemy", map warp). Basically, Gordon uses his powers and knowledge of physics to their logical deadly end. The G-Man recognizes Gordon's potential towards the end of Half-Life, so he reacts him for the inevitable war with the Combine, but there may be a secret Kryptonite to Gordon's abilities: they are only activate for limited periods of time and are more than likely limited in ultimate quantity (much like Spawn's energy powers).

Gordon is an Active.
The senior officials at Black Mesa (above Dr. Breen) knew that a resonance cascade was a possibility. So they hired a Doll who believed he was a scientist, but had latent combat skills (similar to Echo in "Stage Fright").

The G-Man is mostly benevolent
He is infact an alien from a world enslaved by the combine in human disquise, his odd speach and looks are because of his unfamiliarity to humans and their communication. Like the Galaxy Quest aliens, he thought that human media showed they had traits that would mean they wouldn't bend over against the Combine and instead defeat them completly. He caused the Black Mesa incident to bring the Combine to Earth so they get defeated. Freeman attracts the G-mans attention because, like Shepard, he excelled at fighting Xen and the G-Man decided to be use him as strategics weapon against the Combine.

The G-Man is a Combine scout.
He found earth and found it to be a good resource planet for the Combine. He started the Black Mesa incident to signal his masters. Soon he realized that he maniplulates The Freeman he can take over the Combine by having him kill his masters or had a change of heart and regrets his actions, helping The Freeman to remove the Combine once and for all.

Gordon Freeman is the God Emperor of Mankind.
Shortly before the events of the first game, the Emperor decided to try to guide humanity more directly by helping to advance science. The disaster that resulted after the Resonance Cascade convinced him to butt out (once he'd fixed things), and he went back to guiding from the shadows until finally deciding to found the Imperium of Man. The G-Man, given his machinations and manipulation, is Tzeentch, or an avatar of Tzeentch.
 * No way the Emperor would be led around by the nose, even by Tzeentch. But Gordon could be a Primarch, or even the Emperor's earliest experiments to make superhuman soldiers.

Half Life and Team Fortress 2 take place in the same universe.
If the Engineer had just shared his teleportation tech way back when, all this mess could have been avoided.
 * Alternatively, he did share it, but either he didn't proplerly explain details that he considered obvious or he died and someone just found his old notes and blueprints with a similar lack of detail, and other scientists failed to properly recreate it.
 * Alternatively, Gordon is the Engineer. Spending time with the Demoman and the Soldier taught him greater proficiency with more firearms, and he doesn't talk because folks made fun of his accent. That's why he was working on the teleporter project -- it's his project! The only reason he can't build turrets? He has a crowbar, not a wrench.

Valve will include references to Half Life: Full Life Consequences in their next game.
Have you seen how popular it is? They might make something along these lines: "Rebel 1: It's time for me to live up to my family name and face Full- Rebel 2: What the hell are you saying? Rebel 1: It's a family mantra, if you say it, you're guaranteed to not need bullets in battle, because they are so slow at points! Rebel 2: John, I just don't understand you."

"Rebel: Aw, come on, how are we gonna make it over this ravine? I don't suppose that suit of yours has a grappling hook?"
 * They'd better damn reference Concerned as well. At the same time, if possible.
 * They already did. In Episode One you can hear a rebel saying that he misses Dr. Breen's T.V. show.
 * It had juggling.
 * And if I don't hear a Freemans Mind reference, heads are gonna roll.


 * I would abate to that Episode 3 is (I think) going to center around the Borealis, so maybe Alyx could ask if Gordons suit has a Grappling hook
 * I can hear it now. Gordon leads some Rebels across a landscape. One of them interjects. "This the same hill we were at afew minutes ago! We're walking in circles again!"

Gordon Freeman is Jesus.
He's the son of Morgan Freeman, who is God, and is therefore Jesus saving humanity from the alien overlords. And the G-man may or may not be Satan. This also explains the God Mode cheat. And Alyx is Mary Magdaline.

Gordon Freeman suffers from the same issue as The Narrator from Fight Club.
The G-Man is his Tyler Durden.

Dr. Gregory House's near-death experience was in fact, the entire Half Life universe
We all know that House loves video games, so when he shocked himself into a near death experience in one episode, instead of having a religious journey, he played his ideal video game. He was a mute hero with working legs, able to solve greater puzzles than those provided by modern disease. The fact that he is mute is an allusion to how House would have more friends if he said nothing than if he made fun of people any longer.

The G-Man is Light Yagami.
He didn't die, per se, but went from a whole life to half of one, in another reality. Considering how good he is with planning things, and ensuring his plans work even when they don't, he became the G-Man in this reality. His behaviour regarding the vorts taking control of Gordon Freeman was just a ruse so that the Vortigaunts wouldn't realize it's what he wanted them to do. With the help of the Vortigaunts, Gordon was able to get to White Forest and ensure the rocket would be launched, which would ensure that the Combine would react with the murder of at least one top official in the rebellion. This would ensure the rest of the rebels would not stop fighting until the Combine was destroyed across the entire reality. Things are going... Just As Planned.

Father Grigori survived.
Because he wasn't a mere man, he was just masquerading as one.
 * OR he and Gordon did a better job of clearing out the zombies in Ravenloft than we are led to believe, and after you left, he finished off the few that were still following you,and had a very casual stroll back to his church.

The experiment in the first game was an attempt to duplicate Dr. Manhattan, with Gordon as the unwitting test subject.
It didn't quite succeed, but years later, the weapons scanner gave Gordon the kick to temporarily tap into his cosmic powers and melt people.

The G-Man is the BLU Spy.
Seriously, the similarities are amazing: they both wear a blue tuxedo, they have a similar physical build and facial structure (check out the cheekbones! The nose! The eyebrows!), and he is always carrying a briefcase reminiscent of the one the Team Fortress 2 characters fight over. Besides, his ability to turn invisible explains how he seems to just disappear by turning a corner as well as how he just pops up out of nowhere, and his ability to disguise as enemies explains how he didn't get killed by soldiers/Combines/Resistance members/Vortigaunts. Heck, his habit of smoking could even explain how his voice got deeper!

Alyx was heavily genetically modified.
This is the true reason for her regeneration, durability and her understated reaction to getting shot. She is completely unaware of this and thinks she's more or less normal.

The different-looking Vortigaunts from Episode Two are younger Vortigaunts
There are all kinds of stuff to back this up, mainly the smoother skin and the higher voice.
 * It also explains why the Vorts in Episode Two seem to be genuinely reverent of Freeman, as opposed to their subtle mockery of him before then, the elders having seen this before (perhaps with the Nihilanth) and thus don't view Freeman as particularly unique or special, while the younger Vorts are far more idealistic when considering him.
 * Basically Jossed as of a recent update, which makes all HL2 Vortigaunts look the same as the ones in Episode Two.

Gordon Freeman is an Eldritch Abomination
That thing shaped like a physicist that you talk to? That never speaks, eats, or sleeps? That can survive amounts of physical punishment that would destroy armored tanks? That has single handedly, remorselessly, slaughtered thousands of people despite no apparent training or aptitude? And that, for some reason, despite having never met him, people feel an overwhelming sense of trust and confidence in? Gordon Freeman is the gun toting version of Stephen King's Buick 8.

Gordon Freeman is Snake Eyes
Well, have you ever seen Snake Eyes' face? No. No, you haven't. Therefore, theory valid.

Half-Life takes place in the world of Watchmen.
After Dr Manhattan left earth, and the situation between the USA and the USSR stabilised, the real Eldritch Abominations started taking notice of our Insignificant Little Blue Planet as scientists attempted to continue Manhattan's research into teleportation, discovering that the border world Xen was used by Manhattan as a dimensional slingshot whenever he teleported things, unknowingly attracting the attention of the Universal Union. The Combine's typical ponderous sluggishness meant that Black Mesa's resonance cascade happened before their attempted invasion, making it easier for them to invade.
 * At the moment, I'm supposed to be writing an essay.
 * There's a WMG for Watchmen suggesting that the scientists who created the Intrinsic Field Remover that created Dr. Manhattan went on to found the Black Mesa Research Institute. The door locks with Dr. Osterman inside, and it's a saftey feature.
 * Sounds more like they were owned by Aperture Science. Black Mesa is incompetent and stupid. That's outright mad scientist level hostile, which sounds like something Cave Johnson would do.

Solid Snake was in the Weighted Companion Cube.
After the Combine invasion Snake eventually joined the resistance. Eventually Kleiner and Otacon send Snake on a mission to retrieve the remains of Aperture Science technology for the resistance, infiltrating the facility in a Weighted Companion Cube...
 * Which neatly explains why Administrator Breen waited so long to attack the rebels directly because he was trying to avoid a direct confrontation with Solid Snake, the Combine didn't strike against the rebellion until they were sure Snake wouldnn't be a factor.

Half Life takes place in the same universe as the Cthulhu Mythos.
Granted, the means are more scientific than arcane, but something as powerful as the Nihilanth would almost have to be a Great Old One. The experiment with the Xen crystal just gave it a pathway into our world, and of course other critters from that realm are going to leak through. And of course, once it saw what a fascinating world we had, of course it was going to send its slaves (Vortigaunts) and creations (headcrabs, alien grunts) through to check things out. Yes, soaking up Gordon's entire supply of ammo in the endgame hurt a lot. It was being shot in the brain. No, it's not coming back. Why? Because it got pwned by one guy. Unfortunately, this means that Gordon isn't going to be able to kill the real Big Bad behind everything, only force it back into its own realm and shut the door for the time being.

Gordon Freeman is suffering from PTVD.
It's an incredibly likely scenario. While from a gameplay perspective keeping him from speaking would allow the player to identify with him and personalize his experiences, in-universe being bounced around between dimensions, being attacked by creatures both terrestrial and alien, dropped in nuclear waste, trash compactors, shot at, bombed, and generally put through hell, he could very well have developed post-traumatic vocal disarticulation.

Doctor Breen was brainwashed.
Even to the bitter end, he's telling Blatant Lies about serving humanity and furthering their progress - and seems rather earnest in that. It's possible he got exposed to something similar to Room 101, except instead of being executed, he's their new leader.
 * Humans have an incredible capacity for self-delusion. It's probable he genuinely believed the "immortality" and "ascension" claptrap in the beginning, but as the horrors of Combine rule became more self-evident he would have had to systematically deactivate the reason portions of his brain to prevent reality from contradicting his preconceptions.
 * Known in psychology as belief perseverance. It happens as a coping mechanism after we find out that we're wrong about something, so in Breen's case, it could be keeping him from realizing he's made a huuuuuge mistake...

The Vortessence is The Force
I seem to remember one of the Vorts saying something like "there is a disturbance in the Vortessence", but I may be wrong.

Adrian Shepard ends up in the Mass Effect universe.
...and somehow becomes Commander Shepard.
 * Or maybe it's even the same universe and the Gman kept him in stasis for longer than Gordon. The codex for Earth mentions something about environmental damage sustained during the 20th century...I'd say taking part of the ocean would count.
 * So does this mean that The Combine are The Reapers?
 * This could explain the 'Profile Reconstruction' at the start of Mass Effect 1: Adrian has been in stasis so long that his personality and looks have to be reconstructed.

The series will ultimately end with Gordon killing the g-man.
Think about it: This is the guy responsible for EVERYTHING THAT HAS HAPPENED. The Vortigaunts have shown themselves capable of suppressing him. Gordon kills the shit out of anything. Put 2 and 2 together.

At some point, the G-man regains control of Freeman.
To show this off, the G-man will try to make Gordon kill his friends. This either results, as the above WMG suggests, in Gordon arranging an intimate meeting between the G-man's mouth and Gordon's shotgun, or one hell of a downer ending.

Father Grigori is an older version of The Heavy.
Let's see...
 * Both are Russian.
 * Both are extremely powerful.
 * Both name their gun.
 * Both are bald.
 * Both are of questionable levels of sanity.

Lamarr is not one Headcrab, but one of many.
After Lamarr jumps into the teleporter, it (as the concept of Headcrabs having genders is both unfounded and disturbing) can be seen attacking birds on a beach and is left there when Gordon continues teleporting, yet after Nova Prospekt it appears to miraculously return. This is because Kleiner found another Headcrab, de-beaked it and called it Lamarr. He has done this numerous times after Lamarr dies, wanders off or is simply "removed" by a concerned-for-his-nervous-system Barney, either refusing to accept the loss of his beloved pet or simply being completely batshit insane. If there is another Lamarr in Episode Three this will have been confirmed, since being shot into space is not something that is easily fixed.

Episode Three will end in Gordon royally screwing things over for everyone.
Probably stating the obvious here. It's one of the consistent themes of the series (the Resonance Cascade, killing the Nihilanth, instigating the Combine to raid Resistance strongholds, destroying the Citadel's Dark Fusion Reactor) and the first Half-Life ends with the biggest screw up of all, so it is only reasonable the Half-Life 2 story will end with one as well. Considering Eli's warning it will almost certainly be caused by the technology hidden in the Borealis, which itself is almost certainly portal technology. I predict that Gordon will use it to end Combine presense on Earth once and for all, targeting all Combine Advisors by focusing it on one in particular (which of course will only be achievable after defeating it in combat) and killing them all simultaneously. In doing so however another Resonance Cascade will be created, this one making Earth vulnerable to numerous dimensions and worlds instead of merely Xen or the Combine Overworld, turning Earth into the battlefield for a Battle Royale With Cheese with every alien species looking to dominate Earth or fill the power vacuum left by the Combine. Gordon will, of course, slaughter every last one of them, but only until Half-Life 3.

Headcrabs rapidly reproduce asexually
There are hundreds of headcrabs and zombies in Ravenholm, not to mention those that would have been killed before Gordon arrives, yet there are only a few headcrab shells (and there isn't large amounts of structural damage to indicate there are shells buried within buildings). This is because throughout their life Headcrabs emit spores or an equivalent that can produce an entire Headcrab each, provided they have access to sufficient resources. A Headcrab that has acquired a host produces magnitudes more spores as it drains the host and uses the host to more easily acquire more food, sometimes draining the host at an absurd rate (Fast Zombies), sometimes also growing Headcrabs directly from the host (Poison Zombies). With the mines underneath Ravenholm providing them with refuge (note the massive amount there), the relatively few Headcrabs delivered by the bombardment bred and infected the town rapidly, eventually causing what the player witnessed. This was repeated in City 17 after Combine control was crippled, Headcrabs already having used the underground to breed and shelter but now able to spread their infection further. With enough time and resources a Headcrab can become a Gonarch, able to produce immature Headcrabs instead of spores and at an even faster rate, but these are incredibly rare due to most Headcrabs' short lifespans.

Alyx sent Gordon into Ravenholm for selfish reasons.
After being separated from Alyx, she immediately tells Dog to open the Ravenholm tunnel despite at least one route still available. This is because, either due to knowing people in Ravenholm or even living there at one time, the town is a source of great anger and frustration for her, and having heard the stories of the great Gordon Freeman likely directly from people who survived Black Mesa her subconscious mind creates the idea of sending Gordon there to "clean up", so to speak (perhaps not knowing that Grigori was doing the same thing). Her conscious mind however rejects the concept of intentionally putting Gordon in harm, thus her thoughts originally only manifest as a comment that "we don't go there anymore", despite her having no reason to mention Ravenholm. When the Combine attack and the two are separated, suddenly she is given a justification, and she latches to it as firmly as the Headcrabs she sends Gordon to exterminate.
 * Or Alyx sent him into Ravenholm as a test of his strength. She finds the stories of the courageous Gordon Freeman difficult to believe, and so she sends him somewhere that she knows to be extremely dangerous, subconciously trying to test him, to see if he really is the superman that everyone thinks he is.

Gordon Freeman has one superpower.
Everything in front of him that shows even the slightest resistance is destined to die. Gordon can change the very fabric of existence to ensure his survival and a body count rivalling a small nation.

Gorden Freeman is a zombie goast
This is why he is so resistant to attack; he is a goast. Also, a zombie.

Gordon was tested by Aperture Science before, and escaped like Chell
With the new Portal patch adding a bunch more WMG fuel and possible Portal-Half-Life links how about this for an insane theory? Gordon was part of Aperture science testing in his past (although not necessarily tests related to the Portal gun). At some point he escaped and, after discovering a talent for science, joined Black Mesa just to spite Aperture. When the events of Half-Life 1 went down the Training From Hell Aperture gave him inadvertently resulted in him being a Badass One-Man Army and allowed him to bring the situation under some sort of control and survive the subsequent Combine invasion.

One of the new sound files, when reversed, sounds like "Gordon, you're next". This could be Glados, who wants revenge on Gordon for some transgression against her in the past; maybe he was even a contributor to her insanity. This goes into Portal being an Evil Plan by Glados to escape into the "real world" and hunt down Gordon. Of course she'll be very happy when she finds out he is en-route to an Aperture Facility where Gordon is at her mercy... Until Alyx, The Combine, newly-freed Chell and Gordon's own unexpected competence combine to throw a colossal Spanner in the Works of course. The G-Man probably set this all up to sabotage the Combine's plans for Borealis.

Gordon Freeman is dead
He died when he was performing the simple experiment, and the rest of the series is his fever dream while the medical team at Black Mesa try to revive him.

The Combine is a multiuniversal corporation
The Combine aren't The Empire, but rather a Mega Corp that controls countless worlds for the sole purpose of harvesting resources. It's military is used to keep their grip on their worlds. The Advisors are Corrupt Corporate Executives, and the Planet Administrators Pointy Haired Bosses. Considering the Combine's high-tech appearence and cold blue motif, it may even be the BLU Corporation, only from the future.

The Pulse Rifle was designed to be a light machine gun
I get that this WMG very much Mood Dissonance, but bear with me. The combine Overwatch uses three main small arms: the MP7, the SPAS-12, and the pulse rifle. At a first glance, the pulse rifle appears to be a modified assault rifle-it's bigger than the MP7, fires a more damaging round, and is more accurate at range. However, there are problems with this theory, mainly the fact that the gun is way over sized for an assault rifle, and the fact that only one soldier in each Overwatch squad actually uses it. This might be justified during close-quarters battles during the battle of city 17, but the same squad setup is used by the combine outposts on the coast, where the poor accuracy of the MP7 would be fatal if an Overwatch squad enters battle with the rebels at any range beside what is effectively point-blank. It's also worth noting that the gun has ridiculous amounts of recoil-more than most assault rifles. Why? Because the pulse rifle was designed for one thing-suppression fire. Accuracy is unecessary when your role in the squad is literally to provide A-Team Firing, and only one soldier in most modern squads gets issued a light machine gun. And not only this, but in several places in Half Life 2, Gordon encounters a mounted machine gun variant of the pulse rifle. You don't modify assualt rifles to serve as mounted machine guns. And while the rebels in white forest call it the AR2, the name the half-life wikia gives it is the Overwatch Standard Issue Pulse Rifle. And why does the overwatch elite use it exclusively? Not that in every First Person Shooter game ever ever made, the most dangerous enemies are always the ones using machine guns.

TL;DR: The pulse rifle is based off world-war two era machine guns.

At the end of Episode 3, Gordon (and the player) will have to make a Sadistic Choice
...A choice between saving humanity or saving Alyx.

Let's go over the facts.

It's no secret that there's a growing relationship between Alyx and Gordon. Even Valve's own commentary suggests it, as well as commenting on how they have tried to create a bond between her and the player at every opportunity. And they've done a good job, as I'm sure everyone here can attest.

At the end of Episode 2, Eli warns Gordon of the dangers of using the Borealis, hinting that it has the potential to create another resonance cascade, thus dooming all of earth. His last words to Gordon are to "destroy that ship!"

A recent interview with Gabe Newall himself indicates they want to "broaden the series' emotional palette." When asked what will draw the best response, what players fear the most, he responded, "The death of their children. The fading of their own abilities."

With these facts in mind, the final climax practically writes itself. Gordon and Alyx fight their way through the bowels of the ship, planting explosives to destroy it. They separate or are separated somehow, either to draw away the Combine or because the Combine force them apart. In the end, Gordon escapes, but is confronted by none other than a Combine Advisor, as in this picture. As the final boss, it puts up a hell of a fight, delaying the player for many action-packed minutes. But in the end, those few minutes wreck everything. Alyx is still trapped on the Borealis; the ship has been activated by the Combine, and they're preparing to open a portal which will allow their forces through in planet-consuming droves.

Now both Gordon and the player find themselves in a no-win situation. This is not a problem they can force their way through with a crowbar. Their combat abilities will do them no good here, and they must make a choice which will doom their children; either Gordon and Alyx's potential offspring, or all the children of the human race. So, what will it be? Fulfill Eli's last wish and destroy the Borealis, or save your companion/love interest? If Valve really wanted to screw with us, they could put a timer on the decision. One can only imagine...


 * That. Is. AWESOME
 * Indeed - plus, since Gordon's life was 'woven' with Alyx's during the vortigaunt ritual that saved her life, having to sacrifice her for any purpose might quickly turn into a self-sacrifice as well...

Gordon will have to become something similar to a Combine Elite in episode 3.
Because a "And Then John Was A Zombie" moment would win so hard. Plus, it makes sense that only and Elite or an Administrator could meet with an Advisor face to face.

G-Man created Gordon to take out his various enemies.
Warning: There's so much spoilers in here that it was almost unreadable with proper tags, so instead this warning will have to suffice.

So here's how it works. G-Man is asked by his superiors to deliver the sample that causes the Resonance Cascade. The G-Man gets a better offer from the Combine to weaken both sides enough that an invasion would succeed, but his superiors won't let him directly interfere. To get around that, he carefully and quietly inserts Gordon, who is the perfect "right man in the wrong place". Gordon kicks lots of ass, but then various factors (mainly vortigaunts interfering and the G-Man underestimating his creation) let Gordon slip away. Gordon kills the Nihilanth, which severely weakens Xen, which lets the Combine invade but interfers with the G-Man's plans to screw over the Combine later. In the brief chaos following the Nihilanth's death, he manages to regain control of Gordon and lock him up fast. He waits until the resistance is at its strongest, then drops him right in the middle of it. This lets the rebellion do serious damage to the Combine. Then, right when he feels like enough damage has been done, he tries to pull Gordon out. The Vortigaunts are on to his tactics, though, and quickly contain him. He is forced to release Gordon, and the Vortigaunts take control of him. At some point around this time, he comes up with the plan of using the tech of the Borealis against the Combine. The Vortigaunts, thinking that he's trying to help the rebellion this time, get a little lax with containing him. Eli tries to stop him, so G-Man gets a couple of Advisers to slip in during the chaos, set up an ambush in the hangar, and kill him. The Vorts are probably already on his ass by the time Eli's body hits the floor. I predict that the Borealis will not only damage the Combine, but also endanger humanity as well, just as one last big fuck-you to the world on the G-Man's part.

tl;dr G-Man is a textbook Magnificent Bastard.

Opposing Force actually is about a soldier's descent into madness.
Shepard is a fresh recruit who has never seen combat before, so he freaks the hell out when things start going wrong. The aliens, the dead and dying soldiers, the isolation from the main force, all combines to make him go completely insane. He starts hallucinating vividly (Race X, which are actually just various Xen aliens) and develops severe paranoia after he's caught up in a friendly fire incident between some Marines and Spec Ops troops. After he and a group of what I assume are deserters murder several squads of friendlies, he is then identified by a survivor (or by one of the "friendly" soldiers who realized it was an accident) as a traitor to be shot on sight. Some soldiers have lost radio contact, though, so they at least partially believe the ranting lunatic who says the guys in black are hostiles (especially when they actually start shooting). As he gets deeper and deeper, he becomes more and more delusional. He thinks he has a machine that can travel to Xen, and he mistakes a grenade launcher for an alien creature. He finds the nuke, thinks he disarmed it (even in the hallucination, he skips several steps) then imagines he sees a man in a suit rearming it. Eventually, he runs into a Pit Monster that has recently emerged, which his mind distorts into a bizarre mutation of it. Using a pair of nearby heavy-caliber turrets (which may or may not exist), he tries to engage a perceived "weak spot" on the monster. This weak spot roughly corresponds to the mouth of the Pit Monster as seen in Power Up, so eventually he bores through its skull and hits something vital. As it dies, falling debris hits him and causes brain damage of an unknown extent. The G-Man is seen throughout the whole game watching, a manifestation of Shepard's paranoia. He dies thinking that he has been taken prisoner, when in reality he is crippled, unconscious and bleeding alone (not counting the guard upstairs) in the bowels of the facility. A very depressing tale.

It also allows Valve to retcon EVERYTHING.

Duke Nukem is the future Gordon Freeman.
When Half-Life 2: Episode 3 finally comes out Gordon will defeat the Combine by nuking 'em. This particular strategy will earn Gordon the nickname Duke Nukem. Now having saved the planet twice over, he will gain significant fame in the post-reconstruction world, his ego will to swell to enormous levels and he'll even write an autobiography entitled "Why I'm Great".

He'll abandon his friends, dye his hair and shave his beard, then to suit his new "Hollywood" persona he'll ditch his glasses for a pair of prescription shades (Why he didn't wear them before Duke Nukem 3D is anyone's guess.) He no longer has the HEV suit because it was either damaged beyond repair or he donated it to a museum. His muscular physique is entirely logical considering the running and gunning he did fighting the Combine and the reason behind his constant one-liners is that he's seen far worse.

When Duke Nukem Forever/Half-Life 3 finally comes out Gordon Freeman, or "Duke Nukem" as he now calls himself will come out of retirement, pick up a modified HEV suit and face off against the G-Man's forces.

The Suppression Field is controlled via chip implants.
Look at one of the burned corpses, and you will see a bright orange square embedded in the back of their necks. This is probably a computer chip attached to the nervous system that suppresses sexual urges via a signal from the Citadel. Trying to remove it would be fatal, since its attached directly to the spinal cord.
 * Kleiner's speech in Episode One states that the suppression field works by preventing embryo formation, however that doesn't exclude the Combine also suppressing sexual urges, which may be the purpose of the chips.

Headcrabs are a manufactured species.
Why would an alien parasite evolve to attach itself to an animal not native to its homeworld (humans)? Given that alien Grunts are made in factories, it's more than likely that headcrabs were genetically altered creatures (probably little tick-like bugs the Vorts would eat) made by the Nihilanth specifically for invading Earth.
 * Makes sense but for the fact that the Xen aliens and the Nihilanth found earth in a stroke of good luck when the resonance cascade ripped a hole bettween the dimensions, unless the whole thing was a Plan gone wrong for the Nihilanth (possibly Out Gambited by the the G-man) then I doubt it would have known that there was going to be a resonance cascade that lead to earth.

Headcrab saliva contains a powerful bleaching agent.
That explains why headcrab zombies all wear white shirts.
 * The standard city slave uniform comes with a white shirt underneath the blue jumpsuit. Since all the zombies wear blue pants and boots identical to the uniform, presumably they shed their jackets after/while being attacked by the headcrab, or it just got torn off.

The most dangerous/useful thing in the Borealis will be GLaDOS
ASHPD portals would be interesting in the mainline HL universe, but there's no telling what nasty surprises a very misanthropic AI might have developed since it was abandoned.
 * As of Portal 2, GLaDOS is still in the Enrichment Centre, so no, she will unfortunately not be meeting Freeman.
 * Then again, she has enough backup personality cores to fill a warehouse, so her appearance is not outside the realm of possibility.
 * Better yet, how about a secondary (in case of problems) backup of a certain little moron?

Every new Half-Life game takes place in it's own universe
Think about it, the differing zombie designs between Half-Life 1 and 2 (hell, the high-def model pack could even have it's own universe). In regards to episode 2, there's the sudden appearance of a new character in episode 2 who everyone treats as an old friend, the small differences in the HEV suit's systems, and the sudden replacement of the old vortigaunts from Half-Life 2 with the younger looking ones. In addition, the recent update for Half-Life 2 (the one that ported it to the Orange Box engine and added Macintosh support), due to the appearance of the ammunition icons from episode 2 in the HEV suit's HUD and the episode 2 style design of the vortigaunts, could be said to have put HL2 essentially in a universe somewhere between that of the non-Orange Box version of Half-Life 2 and episode 2. I have absolutely no idea how episode 1 fits into this theory, though.

Adraian Shephard will be in another half life expansion pack: but not in the main seiries until a cameo in Half life 3
Just look at it like this, a load of people love him and want him in a game, but valve already destroyed aby hopes of having him in episode 3. Valave want to please their fans so either they or gearbox software will make a sequel to opposing force, it'll take place in the same universe and the same time but Gordon Freeman and Adrian Shephardwon't meet until Half Life 3 and when they do there will be a showdown to finaly determin which is best. The Crowbar? Or The Wrench?

Alyx's mother was turned into a Stalker.
Or possibly an old boyfriend of hers. Just look at her emotional explanation of how they come to be.

"This is what happens to you when you resist... Or if you're just in the wrong place at the wrong time."

The later enemies in the half-life series are caused by sleep deprevaition
Gordon is spending days in that suit trying to stay awake and succeeding because of the adrenaline pumping into his bloodstream fueled by the suit but by the time he gets to xen a majority of what he sees is manifestations of long term lack of sleep (you explain an armored monster that shoots bee things out of a living tentacle), in fact he could have been missing sleep since before the game started explaining why you don't talk (sounding like a moron or not having the energy to move your jaw) or can only do rudimentary tasks like push buttons, pull cords and open doors. This is supported because the sky-box changes throughout half-life, 2 and the episodes hinting at multiple days elapsing.

Gordon Can Speak.
He just dosen't want to, nor has found a good reason to
 * And it's not like he ever has enough time to say anything before the next alien crashes through a door or wall collapses near him. The guy's a serious Weirdness Magnet.

Antlion Guards are the 'male' Antlions, and the Bugbaits are gonads.
In nature, the male members of a hive-based insect are usually meant to be able to survive the trip to a queen's chamber. The Antlion Guard is armored appropriately. The Bugbait you pick up is loaded with pheromones that attract Antlions. Most hive insects have females as the general workhorse. As such, Bugbaits attract female Antlions. This means that the Bugbait is a sexual gland used in mating. Additionally, one of the Rebels at an outpost says that it is the Antlion spawning season, supporting this claim. Also, Valve would absolutely use this sort of humor(Gonarch, anyone?)

G-Man is a super computer AI
G-Man is the male counterpart to GLaDOS, produced by a secret Black Mesa project. While Aperture Science has mastered spacial manipulation (portal technology), Black Mesa has mastered time (G-Man time-manipulation technology). Thus, all of G-Man's apparent teleportations were really just clever time manipulations. In the end, only a combined mastery of time AND space can bring and end to the Combine empire! This has all been brought about by the human resistance themselves in the future, who send G-Man back in time to create a stable time loop where the time and space manipulation supercomputers are created and deployed perfectly.

Humans are on the brink of extinction
Probably stating the obvious here. Considering that by Half-Life 2 there have been almost two decades of not only no human reproduction whatsoever, but also the planet overrun by vicious, incredibly numerous and deadly aliens that kill without hesitation, the Combine converting who knows how many people into soldiers and Stalkers and outright killing many more, and the untold millions that would have died from starvation, infection and general things resulting from the collapse of human civilisation, well, the numbers don't look good. With the Uprising killing many more and with most humans probably now evacuated from the cities and living in the alien infested wastelands, those numbers are going to drop rapidly before anyone even has the opportunity to reproduce.
 * Note the Seven Hour War is named that because it lasted seven hours. I doubt that many would starve to death in that time. The war would be officially over once the Combine had taken over literally all of Earth, and the Combine give food to their citizens. Why anybody would starve to death during that time, I don't know.

The Borealis is not going to contain portal technology, but time travel technology
While their colleagues at the Enrichment Centre were busy screwing with space, the Borealis crew were busy screwing with time, one of their experiments accidently launching them twenty years or so into the future (which explains why no-one discovered the vessel until then). With this shiny new weapon (because really, what isn't a weapon when Gordon is involved), Gordon is either going to return to Black Mesa and stop the Resonance Cascade from occuring (unlikely, considering he wouldn't have freed the Vortgaunts), go to the beginning of the Seven Hour War and fight against the Combine before they conquer Earth (which would make an excellent setting for Half-Life 3), or, my personal favourite, simply erase the Combine from existence altogether, because that is how Gordon Freeman rolls.

The Combine only manufacture and use very low-powered weapons.
All of the Combine standard issue guns (including the Usp Match, SMG 1, Pulse Rifle, and Shotgun) are unable to kill in one shot (except for secondary fire and point-blank shotgun). This in itself might not seem like much, and could be attributed to being this way for the purposes of game balancing. However, all of the rebel-made and used weapons (Magnum, Crossbow, and RPG) kill in one shot. Surely the all-powerful Combine would be able to make something more powerful than an improvised crossbow? My guess it that they avoid this lest the weapons fall into the hands of the rebellion. Considering their tight control over the world, they would not have much use for more powerful guns because they are effectively facing unarmed citizens (at least until Gordon arrives). Therefore, I think that they have deliberately made their guns to not be overpowered so that they cannot be turned against them.

Lamarr is Kleiner's pet cat.

 * Kleiner once tested the teleport on his own pet cat, and (possibly because of some headcrab DNA being thrown into the mix) it was transformed into a headcrab. The process of the cat changing was probably what gave Barney nightmares. It's why Kleiner cares so much about the headcrab, despite it being a monster which can turn a human into a shambling zombie.
 * Alternatively, Kleiner just thinks that Lamarr is his cat, and she's really a random headcrab picked up by the teleport. The cat is probably dead.
 * This could mean that the universe the headcrabs teleport in from is actually full of cats, they just become headcrabs in the process of getting here.

There is no Combine Master Race
The Combine were a group of different species from day 1. They started out as a small organization of cyborgs from different species and just kept growing and growing until they became the vast inter-dimensional empire we see today.

Headcrabs can only zombify certain groups of humans.

 * In many places, you see headcrabs attacking and killing humans without zomifying them, and we know that the headcrabs never zombify Gordon, only try to kill him. This is because only certain humans can be zombified, and Gordon is not one of them.

Reason why headcrabs only zombify humans.

 * In other species (or at least the species they evolved alongside, probably from the Vortigaunt homeworld) it's possible they form a symbiotic relationship with other creatures, perhaps similar to mitochondria only on a macroscopic scale. But whatever they do, they interface with a specific chemical in the creature's body.
 * Now, here's where the theory comes in. Whatever chemicals the headcrabs interface with, the same or very similar chemicals are present in the human brain. Due to this coincidence, the headcrabs are attracted to human brains, and can interface with them, allowing them to take partial control of the human body. The chemicals present in the human brain also causes the headcrab to become extremely aggressive, which is why the zombies will attack anyone living who comes near.
 * It's also possible that the chemicals present in the brain are tastier than the chemicals they normally encounter, and so after gaining a taste for humans, they become addicted- hence why they attack any human who comes near.

Gordon actually has 20/20 eyesight
The glasses are just there to interface with his HEV and act as a helmet would insofar as the HUD is concerned. Also, the project a weak energy field that protects him from headcrab infection. If you notice, they appear to actually have something displayed in them in some of the artwork, likely part of his HUD.
 * Either that, or he just wears them to look smart.

Father Grigori used to be a mass murdering psycho.
He claims that his traps are "the work of a man who once had too much time on his hands... and now finds time for nothing but the work of salvation." This implies that he constructed the traps BEFORE the zombie crisis happened. What do you call a man who deliberately arranges numerous death traps all over a lively town filled with innocent citizens? After the bombing happened, he was so moved by this that his mind suddenly reverted back to normal, realized what horrible deeds he had done, and promptly went batshit insane again - though in a different way.

The reason the people from Black Mesa East stopped visiting Ravenholm is because Father Grigori (who, like Gordon and Alyx, seems to be one of the rarely-encountered individuals who are born Made of Iron) took over the town, killed or imprisoned most of population, and set up traps to hunt down the survivors.
 * So... Father Grigori is actually Jigsaw?

The G-Man created Gordon
The G-Man wasn't allowed by his superiors to directly influence the situation. In order to get around this, he managed to create a man with the right skills who's always in the right place at the right time without any of his superiors noticing. His superiors did notice that Gordon was singlehandedly stopping the entire Vortigaunt army, though, so they had him put in stasis. Then 15 years later the G-Man tried slipping him in again. He was caught and forced to return Gordon before he did any permanent damage. Then the Vortigaunts intervened. He's been subtly helping the rebellion (he tried to warn Eli, he saved Alyx, and various other things) ever since.

The secret ingredient in the Gravity Gun is Element Zero.
Hence the reason the Resistance only has the one, and the reason that they didn't use it in the field until Gordon grabbed it.

Additionally, the stuff that caused the Resonance Cascade was probable unprocessed Element Zero.

Gordon wears one of those geek straps across the back of his head, keeping his glasses on.
Because this guy jumps around so much it's really a wonder that he hasn't lost his glasses yet.

Alyx is a Slayer
Explains her raw endurance, and her ability to defeat zombies in hand-to-hand combat. She doesn't know, otherwise she'd go into melee a lot more.

The G-Man will never be elaborated upon in the same way that the player is never elaborated upon in-game.
In many ways, the player is just like the G-Man... but much, much worse. Gordy has a puppet-master he's aware of and a puppet-master he will never be aware of. Valve just wants us to feel at the mercy of someone you can't understand... but of course, we do in fact have power over the G-Man in that we choose to play his games, something Gordon will never know.

The Half-Life series is a game-within-a-game.
...And the G-Man is the player.
 * It would explain how all-powerful he is, and why his motives don't make much sense- he's just messing around with the game world. He caused the Black Mesa incident because he wanted an alien invasion. He made Gordon a One-Man Army because he wanted a badass character. He blew up Black Mesa because he wanted to be cruel to Adrian. He made the Combine invade because he wanted a war. Gordon is just one of the characters in the game, at his mercy just like everyone else.
 * However, from Episode 1 onwards, some of the video game AI (the Vortigaunts, perhaps others) has become sentient, and is starting to rebel against the player. They (possibly using cheat codes) have been holding the G-Man back, stopping him from interacting fully with the game world.
 * Alternatively, the G-Man is just one of the players in an MMORPG, who uses cheats to mess with the game. The Vortigaunts are admins. Gordon, Adrian and Barney might be players, or they might be NPCs.

The Vortigaunts realize it's all just a video game.
I don't really believe in the above theory, but it did remind me of something very interesting: since the original Half-Life 2, the Vortigaunts have, at times, seemed vaguely aware of the Fourth Wall. Certain cryptic messages of theirs could be interpreted to mean they know they are really just characters in a video game, and that Gordon Freeman is merely the player's avatar. Examples:
 * "Your bright face obscures your darker mask."
 * "Far distant eyes look out through yours."
 * "Could you but see the eyes inside your own, the minds in your mind, you would see how much we share."

Of course, any of those sayings could mean anything. But here's one that really throws all ambiguity to the wind: you know how after the Vortigaunts free Gordon from the G-Man, the mission failure messages you get seem to have been written by them? Well, what sentence shows up on the screen if the player fails to defend White Forest in Episode Two? Answer: The game now ends.

This still doesn't make the stakes any lower for them, though. Remember, the Vortiguants view time and space as "false veils", so the game world is just as real to them as our world is to us because to them, everything is real.

Breen is alive.
We haven't seen him in two games, yet he was a pivotal character in the original Half Life 2. A bit odd. What's stranger, though, is that he mentioned something about a host body. When Breen is mentioned to be dead in Episode One, the next scene is that of the Advisor attack. What if he got the host body in the form of an Advisor, specifically, 314 URB-LOC 0017? It would also be a nice solution in the case of Breen's voice actor, who recently died.

At the end of Episode Three, Gordon will speak for the first time.
And he will tell Alyx he loves her. Think about it.
 * If Valve was any kind of awesome, they'd incorporate some sort of voice command mechanic whereby the player could tell her themself. Come on, we all want to.
 * Seconded! In Half-Life 2, when Alyx and Eli are being carried up to the portal, This Troper wanted to cry out and tell Alyx (as Gordon) that i loved her.

Gordon Freeman is deaf.
He doesn't speak, and Valve have said they'll be including a deaf character in episode 3, who Alyx has a crush on, as an excuse to add sign language to the Source engine. On top of this, the game includes subtitles and closed captioning, as well as facial expressions, body language, and sophisticated enough animation to allow for lip-reading.
 * Alternately: Gordon talks, but for whatever reason, you're not allowed to hear what he says. (Possibly tying into the "Gordon is G-Man" theory, if you heard his voice, it'd be a dead giveaway.) Characters do react attimes as if he's said something.

Gina and Colette will appear in episode 3
Not much evidence for this, but it would probably please the fans, and it would be pretty cool.

Gordon is an android
That's why he doesn't eat, sleep or take a dump at any time during the game. He doesn't need to. That's also why headcrabs do not try to attach themselves to him, and why he volunteers to do life-threatening assignments for the Resistance. He knows that he would be more likely to survive than a human. He refused to believe that Android Hell was a real place and escaped from the Aperture Science lab. His hatred of Aperture Science caused him to join Black Mesa knowing nothing except that they were "rivals" and he became fiercely loyal to them. He later fights the Combine out of this loyalty, which he now displays toward Black Mesa's ex-scientists. They do not know he's an android because his appearance was altered like Andrew's in Bicentennial Man.

Gordon Freeman is multi-lingual.
That's why everyone in HL2 and its Episodes seem to speak English, despite not being set in an English-speaking country. Gordon can understand a wide range of languages, and it's translated into English for the player.
 * This needs to be true, if only because it's too good an opportunity to miss for a character that never speaks to know several languages.

Half-Life 2 is actually an extremely well-thought-out FPS ren'ai game.
Valve's commentary would suggest that the developers are putting just as much time into making Alyx a believable, likeable character as plotting and developing the rest of the story. She's been so carefully written that it's almost impossible to find something to dislike about her, and she hits so many different points of appeal (Action Girl, Wrench Wench, and Break the Cutie, to name a few - this troper pleads particularly guilty to that last one) that it's hard to keep track of them all. The player character is a professional geek in the right place at the wrong time who barely has to do anything for her affection, although this affection seems to grow more abundant the more tasks the player completes. If not for the aliens and zombies running amok in the crapsack future, HL2 could easily be a dating sim - with the addition of those elements, to say nothing of the genuinely amazing writing, it becomes the baddest-assed dating sim ever.

Advisors are weak to whatever metal the Crowbar is made of.
Advisor fights in Episode 3 will consist of weakeing the Advisor enough to get it to Crowbar range, and a few good smacks to the head will do it. Coincidentally, D 0 G's fists and/or the rest of him are made of the same metal, explaining why the Advisors quickly ran off at the end of Episode 2.

The world of Half-Life is the same as Battlefield Earth, but with a credible story.
Just think about it: An invasion from another dimension.

Earth's defense forces wiped out pretty fast.

Earth's resources being drained to an off-world location.

Humanity is facing extinction.

Out comes a hero, to lead a human rebellion. Taking down the main city of the occupation and dealing with its aftermath. This is the story L. Ron Hubbard would've written if he wasn't spaced out on the deck of a boat somewhere.

Shepard is still alive in the world of Half Life 2
I know there are tons of WMG's like this, but just think about it: Where as Gordon Freeman managed to spark a rebellion in Eastern Europe, Shepard was probably dropped by the G-Man into North America. I mean, a worldwide rebellion is mentioned, and there is no way Gordon could've done that alone. Basically, after the BM Icindent, Shepard gained a reputation as a great fighter and the only friendly marine, so he is dropped in North America by the G-Man, where similar events occur that spark a rebellion there, except mainly headed by former marines before the seven hour war, as Shepard is a war hero for singe handedly dealing with Race X (who were part of the combine and the seven hour war), at least until they invaded.

Barney sabotaged the teleporter in Half Life 2
Barney is taking his revenge on Gordon for the Black Mesa incident.After all, he did say, in Half-Life 1, "I'd like to get my hands on the guy responsible for THIS mess." Barney actually trained Lamarr to attack Gordon. Barney also refuses to help Gordon back into Dr. Kleiner's lab (where he'd be safe from people trying to shoot him)and instead gives Gordon nothing but a crowbar and wishes him good luck.

The advisors we see aren't acctually the real advisors
That or they aren't the acctual original combine. So either they're greyish skin is a sort of protective suit and the acctual organism is inside, tender and easialy damaged despite protective fluid. This is probably due to the fact that as they conquered the galaxies they became more and more reliant on technology and thus lazyier and less able to cope, before they retreated to their suits using their phsyic powers to keep themselves floating off the ground and safe.
 * Or the second one, the advisor suits look alot like synth materials. Plus their names "advisors" ,they're probably a race that the origional combine enslaved or alied themselves with them volentarily. Then they got dumped with running newly conqured worlds that aren't considered important and the administration of the combine empire.

Cremators were a scrapped Combine project.
The Cremators were a synth project of the Combine, early in their 'reign' and while they were still experimenting/developing Stalkers. However the project was scrapped after a short while, due to various complications such as not being efficent, or being clumsy to 'manufacture', or a short lifespan/a hasty rate of deterioration due to what was left of the human not being able withstand the prolonged exposure to the acid from their Immolator. Not to mention that there would be a greater psychological effect on the humans if they were living in squallor, rather than having the Cremators clear away the dead. So the survivng Cremators were destroyed and their remains were carelessly dumped. Alyx came across a piece of their remains - a Cremator head, and took it back to her father who preserved it in a jar out of curiosity.

Barney is dead
He wasn't in the last game, and he's fucking annoying, so I hope it's true.
 * "GRENADES, GORDAN!"

The G-Man is the Slender Man
Come on, Its obvious.
 * Okay, unfair. I just got over my fear of both of them.

Left 4 Dead and Half Life take place in the same Universe
The Virus that keeps getting mentioned in Left for Dead is actually a biological weapons agent manufactured by the combine that turns approximately 75% of humanity into zombies. After seeing the Nihilianths forces get killed by a nuke at black mesa, they realized the destructive power of humanities arsenal, so they sought to minimize casualties by weakening humanity by developing the Virus using biological information from the dead scientists at Xen. Humanity was winning the war against the zombies, but only 24% of humanity was left. The Combine then launched their invasion using massive amounts of Striders, Gunships, Hunters, Dropships, and Race X creatures. They overtook the worlds combined military in a matter of hours with light to medium casualties, eventually implementing their new rule, and officially making clearing out the rest of the zombies the new overwatch forces first test. They succeeded very well, which is why there are no live zombies like that in Half Life 2. This could also explain some of the Combine soldiers equipment: The gas masks are to prevent non-immune people from being infected via the air, and the blinking on the hand grenades is to attract zombies like the pipe bomb in Left 4 Dead.
 * Left 4 Dead and Left 4 Dead 2 take place in 2009. We know (from the Half-Life manual) that the Black Mesa incident took place in 200X, which assuming it's concurrent with the Left 4 Dead universe, places it at May 15th, 2009. In Blood Harvest from the first Left 4 Dead, you can observe leaves falling from trees, which indicates that Left 4 Dead takes place in autumn. (Octoberish?). Therefore, the two timelines are incompatible.

Gordon Freeman's symbol is not a Lambda, but a Gimel, the Hebrew symbol of justice and punishment.
"Think not that I have come to send peace on earth: I came not to send peace, but a crowbar."

Alternatively, his symbol is not the Lambda, but the Lambada!
A mistranslation caused everyone to think he spoke Greek, when in actuality he is a dancer.

Grigori is an angel.
Just type Grigori on Wikipedia. What does it translate into?

Here's some proof:
 * He survived the zombie apocolypse and managed to build the traps.
 * He is a religious man, who lives in a church.
 * He has an post-human amount of skill with a shotgun.
 * He never abandons Freeman.
 * He gives Freeman a shotgun, only to produce another, stronger one that Freeman cannot use, as in he is channeling God Himself.
 * He believes killing the infected will save them.
 * He becomes solemn when entering the graveyard.
 * He charges into the fire, but continues to laugh, implying he survives fire due to his holy protection(Shadrak, Meshack and Ebegnigo).

Half-Life: Episode 3 and Duke Nukem Forever will be released together in a Vaporware Pack
Because it'd be funny, and it makes sense. And packs seems to be a growing trend in gaming these days.

All of Valve's games take place in the Half-Life universe
Basically, it goes like this:

Day of Defeat/ Source - WWII. No real relation to main events

Team Fortress 2 - Beginnings of Aperture Science (BLU) and Black Mesa (RED)

Counter-Strike - Terrorists used to keep other nations busy from helping the US during the (yet to happen) Black Mesa Incident.

HL1/Blue Shift/Opposing Force - Black Mesa Incident.

Left 4 Dead - (see above WMG)

Portal - about 2 years before HL2

HL2/EP1-3

Alien Swarm - Simultaneous to HL2, shows Combine forces in other places.

Ricochet - also takes place around HL2. It's some game vorts play.

Gordon Freeman was born a woman.
Just look at how he examines his hands when he first puts on the HEV suit in Half-Life 2.

The G-Man is...
An entity from Real Life created in order to assist Gordon Freeman.

The G-Man is The Slender Man
Or how Slendy appears in the Half-Life 'verse. Think about it, business suit, reality warper, there one minute, gone the next. Face appears differently to everyone that views him. It's a perfect fit!

The Advisors are babies.
Am I the only one who though the Advisor inside its pod looked like a baby tucked in a crib? It even had a blanket!

== The reason we never see Gordon - or any main character - eat, sleep, or use the bathroom is because all of those functions are tied into the medkits and medical stations littered throughout the games. == At least in the HL2 parts. Liquid diets do exist, they're used in hospitals for people who can't eat. The medkits have green liquid inside them. It's not a far stretch to assume that something that can heal a bullet wound might also have some nutritional elements to it too. The reason they don't go to the bathroom? The Combine - with the locations of some of those medcenters they're obviously Combine tools - have had at least fifteen years to perfect a wasteless liquid diet. They've also had plenty of spare "citizens" to experiment on. It's quite possible they've solved that problem, and since a leak at the medkit factory has given the Rebels a healthy supply of medkits, they're benefitting from it too. The lack of sleep could be from a stay awake drug also present in the medkits/centers, which would allow people to stay awake for longer stretches. Only having to sleep once a week, instead of once a day, drastically reduces how many beds you need in a facility like White Forest, leaving more space for weapons and equipment.

Gordon's suit does have a helmet...
But it can be retracted into the suit, and he removes it whenever he doesn't need it.

There, helmet/no helmet flame war solved.


 * This actually explains a lot of things, like why there are no separate helmets available in any of the suit storage areas, and why none of the suit-wearing corpses have the helmet knocked off of them (being attached to the suit). Also, the reason Gordon doesn't activate the helmet in Freemans Mind is because he never read the manual.

G-Man is Satan
He shows up all over the place, even inside unpowered or almost broken electronic devices: A tv and a couple of the big screens scattered around City 17. He can make deals with people, if you take Breen's word for it. Breen would probably know, G-man was at BM when Breen was administrator. Satan isn't God, but he's powerful. The Vortigaunts could have held him off with enough power.

The G-man is Xen's First Guardian

 * The teleporting effects in game one is green lightning, just like the Homestuck First Guardians.
 * G-man changes the scene several times he speaks to you (especially prevalent in the HL2 opening), just like Bec does in his strife with Jade.
 * He isn't a blank white form because that suitcase. if it were destroyed the charade would be up.
 * The Xen session (called Svort) never started because of the resonance cascade and is a doomed timeline that somehow stabilized into its own universe with the doomed timelines of other sessions, including the Earth session (Sburb) and the Combine session (Sbine). The Troll session (Sgrub) is probably there too.

The G-man is Christopher Walken

 * Apparently he has expanded his powers beyond flying.

Portal 2 will end with Chell escaping Aperture Science on board the teleporting Borealis
At the climax of the game, Chell activates some kind of secret massive portal device onboard the Borealis, teleporting the ship (and part of the drydock, according to Eli) to the arctic. The Combine hope to find the ship in order to use its giant portal device.
 * but... portal 2 takes place 100 years after the first portal...
 * When the Borealis vanished from drydock, it was hurled through space and time, so 100 years after the first Portal is the time of Half-Life 2 Episode 3.
 * Both games stories will occur simultaneously.
 * Nope. Part of the dock can be found in a hidden room, but the Borealis is long gone.

Gordon will finally speak at the end of Episode 3
Imagine This: Near the end of Episode 3, Gordon finds himself in a situation where he can easily defeat the Combine in one fell swoop. As soon as he tries, however, Alex ends up being attacked by a Combine Adviser, and is dragged away from Gordon. Gordon immediately gives chase, only to be stopped in his tracks by the G-Man. The G-Man, supposedly having a contract to help the Resistance destroy the Combine, orders Freeman to go back and eliminate the Combine for good. The player hears a cry for help from Alyx. It's at this point control is taken from the player for only one moment, as the camera swings around to show Freeman's face, and he says one word, "No." This could possibly lead to some sort of boss fight with the G-Man for Freeman's 'Contract'.
 * This sounds pretty epic.

The G-Man is Gordon's father.
The G-Man's seemingly bizarre behavior is really just concern for Gordon. However, he doesn't experience empathy or think like a human, so some of what he does doesn't seem to make sense. But from his perspective, all of his actions make perfect sense: Like any good father, he wants Gordon to be safe and happy, but also to have engaging, challenging work. As an added bonus, Gordon's muteness can be written off as a weird byproduct of his non-human ancestry, similar to how mules are sterile.

Lamarr Was Thrown Into Another Dimension
When the rocket Lamarr was in was fired at the Combine portal in Episode 2, it caused a distortion of the barriers which separate dimensions and Lamarr was tossed into an alternate dimension... The dimension of Super Meat Boy!

Gordon will destroy The G-Man with a crowbar
Read the above WMG about Gordon finally speaking.

Gordan will be forced to walk through an Aperture Science Material Emancipation Grid on board the Borealis during Episode 3.
It is supposed to have one, and one of the things that scares us is the loss of our abilities. They said they plan to add that to a future game anyway, and the ASMEG is a convenient way to accomplish it. It certainly would be scary, too, considering that: none of his weapons would make it through, his HEV suit would likely be "emancipated" as well, and it's entirely possible that his glasses could be gone too.
 * Soooo... Gordon's gonna be naked?
 * No. Chell's jumpsuit stays put when she walks through an ASMEG, and it's probably safe to say that Gordon's wearing something similar under the HEV suit. He might have commando training, but I doubt he goes commando -- especially what with all the pinchy bits that powered armor might have on the inside. His teeth are fair game, though.

Alyx will serve as Gordan's anchor...
Now that they're lives have been weaved together, one of three things will happen:
 * When G-Man tried to take Gordan back and put him in status, he won't because Gordan will be "chained" to Alyx. Alyx, who never made a deal with the G-man, can't be taken by him, and so Gordan can't either.
 * When G-Man takes Gordan, he'll end up dragging Alyx with him.
 * Or, most likely, he'll take Gordan away, Alyx will start to weaken and die, so the Vort's and Barney will get in contact with G-Man, and offer Alyx's services (who'll be in a coma by that point) to him in return for her contract stating she has to go everywhere with Gordan.

G-Man is (or was) Charles Foster Ofdensen.
Nobody really knows what's quite up with CFO or G-Man. They are either great protectors or catalysts for something horrible.

G-Man is not Gordon, but his universe's equivilant.
In Opposing Force, the G-Man claims he sees a bit of himself in Adrian, which is why he spared him. Thus, this means that he sees himself in Gordon. But which one did he remove from Stasis? Gordon. It seems as if the G-Man identifies with Gordon, but also opposes him. Why? Simply put, Gordon has one thing the G-Man does not: love. That's right, I just put a Harry Potter Power of Love motif onto Half Life.

To continue, the G-Man sees Gordon as a man of similar interests as himself. He assumes that Gordon will be a mindless pawn, as they would share a common goal. His assumption was that he would destroy Black Mesa, just to save himself. But he didn't. He stayed behind to save his co-workers. This puzzled the G-Man, who did not see why Gordon did what he did. Deciding to do the work himself, the G-Man nukes Black Mesa, takes advantage of Gordon being in Xen, and has the Borderworld opened to the Combine. This would be contrary to his original plan, but as we see throughout the games, his loyalty changes hands, so this may have been the deciding factor in who he worked for.

Skipping forward twenty years, we see the G-Man, once again, believing that G Ordon will work for his new employers. This time, he is correct. Gordon defeats the Combine's earthly leadership, the G-Man assumes Gordon will flee and save himself. Once again, he stays with Alyx. This time, however, Gordon had done his job, so rather than intervene, the G-Man simply let Gordon die, with his "friends", since the job was done.

The Vortigaunts intervened. The G-Man, as Gordon's equivalent, would be able to deal with them if he wanted to. But honestly, who likes to deal with them? Besides, other theories state that they have grwon in power. So he just let them do whatever they had planned for Gordon. After all, improvising had worked for them both. In short, it worked, and Gordon escaped with Alyx. It was then that the G-Man realized that Alyx was more than just a weapon that he picked out for Gordon: she could be used to manipulate Gordon, even if he was out of his control.

As such, he summoned a Hunter upon Alyx, so that not only would Gordon have to follow his path to White Forest, but Alyx could be an exploitable force. To further this, he killed Eli and kept Barney and Izaak far away, so Gordon would only feel loyal to Alyx.

As for what he will do in Episode 3, he will use Alyx to force Gordon into doing something unspeakable. I don't know what it is, but many theories are abound, and my favorite is the Sadistic Choice, so we will go with that one for the time being. He will make Gordon choose: save the world or save Alyx. If he chooses Alyx, which the G-Man knows he will, this will put G-Man or his employers in a position of power over the Combine. Since Gordon is a One-Man Army, he will stop the G-Man and maybe save Alyx, but he will have broken Gordon, hoping that he will turn out just like himself. Will Gordon become the next G-Man, starting a vicious cycle, or will Gordon overcome the heartless mirror of himself? Again, only time will tell.

The G-Man arranged Eli's death.
At the beginning Episode 1, the Vorts steal Gordon away and essentially break the contract made with the G-Man. Obviously, the can't be allowed to happen without some kind response. There has to be some kind of price paid. But who can he use? He can't waste all the time and energy he poured into Alyx and the Vorts don't really care about Barney or Kleiner. Plus, when Gordon goes off the radar, there's the possibility that he and Eli might start to compare notes and complicate some carefully-laid plans. So, the G-Man arranges for the Combine to patrol certain areas he considers likely for Gordon and Alyx to be travelling. He gets lucky and re-establishes tabs on Gordon during the Vortigaunt ritual. Now he can control the situation again and he lets Gordon know it.

But there's more. He implants a message into Alyx in order to provoke a specific reaction from Eli. Thus, after his death, Alyx will be determined to carry out his last wish and destroy the Borealis. Except that there's going to be a snag - it will turn out that the Resistance really will need the tech onboard to defeat the Combine, meaning that Gordon will have to 'betray' her in order to save humanity. This move will end up isolating Gordon and forcing him to once again submit to the G-Man's control and it will be made very clear that Gordon will remain in his employ for the rest of his life.

The G-man is a rogue Observer.
A mysterious man wearing a neat suit, with unknown power, and displaying odd mannerisms? Sounds like an Observer to me!

The G-man is the 10.5th Doctor
Okay, I admit this mostly comes from the suit. Despite being only half Time Lord, he still outlives Rose, and eventually goes mad from watching everyone he knows die but not being able to leave in the TARDIS (or something else, I realise that doesn't make a whole lot of sense). Eventually he loses his former ideas regarding morality and the protection of Earth...
 * ...and strikes a bargain with the Shadow Proclamation, becoming their agent charged with maintaining galactic stability around Earth. He obtained the ability to turn any vehicle into a replacement for the TARDIS -- hence his trip with Gordon in the trans-dimensional monorail car at the end of HL1, and with Shep in the Osprey at the end of OF -- in exchange for his rebellious spirit and, for some reason, his Estuary English accent. His loyalty to his masters means that he's just as willing to work towards the benefit or the detriment of humanity depending on the current balance of power in the galaxy. What little he retains of his old personality drives him to select human "assistants" with whom he has some limited contact.

The Resonance Cascade was the best thing to happen to Humanity since sliced bread
In Half-Life 1, Black Mesa was going to end up destroying itself if it wasn't for the aliens. In Half-Life 2, Humanity was going to end up destroying itself if it wasn't for the aliens.

The Valve games share storylines.
World War Two starts, and this is where things get freaky. The Wehrmacht and Allies of Day of Defeat discover top-secret information, leading to the creation of RED and BLU of Team Fortress 1 & 2. RED and BLU form Black Mesa and Aperture Science, respectively. Meanwhile, Terrorists and their Counter-Terrorist rivals are competing around the globe in Counter-Strike. Gordon initiates the resonance cascade and the 7-hour War. Aperture Science captures headcrabs and studies their zombifying qualities and accidentally releases it into the water supply of City 12. The Combine avoid City 12 and observe from afar for scientific purposes.

G-Man is Gordon's predecessor.
That is to say, he was also a human who went from regular joe to unstoppable ass-kicker. By surviving against all odds and impressing his future employers, he was given a job as their most trusted agent (why else would he be able to convince them that he was right and get away with ignoring nay-sayers) and powers to facilitate his work. After spending countless years working with aliens (and becoming unused to speaking English), he was finally given a job where he encounters somebody who reminds him of himself and could potentially serve his masters as another agent.

The G-Man is Timo Julkunen, the current CEO of Valve.
The entire game is a mutation of the workplace. Gordan is the viewer, the resistance are other consumers, the Vortigaunt/ The G-Man's bosses represent the Board of Directors, and the enemies represent the union.

The Citadel is made to mine planetary cores.
The Citadel is impossibly tall, reaching beyond even the clouds, and digs an unknown distance into the ground. And the machinery seen when entering the Citadel from the bottom gives the feel that it is continuing deeper into the ground. And its doubtful all those yellow pipes running up the building from the bottom are just for show.

The black mesa complex was created as a superbunker during the cold war.
It was made to hold everyone society needed to survive, as well as fire back at any remaining east block areas. All the ridiculously large chambers, such as the crate-smashing chamber, were made to hold ICBM's. The facility produces so much radioactive crap because it was assumed that, when taken in use, the earth would be a radioactive wasteland anyway. The turrets and mines would be automatically activated after the initial habitation of the complex, both to halt any potential soviet remains, as well as stopping people from flooding the facility with radiation by attempting to open the doors. Because it was built to hold so many people, many parts of the complex are now empty and it has an utterly massive waste treatment plant. The walkways were constructed to be as light as possible, so that people could use the areas below it as shelter, while not being harmed by the walkways as they collapsed due to the tremors caused by thermo-nuclear weapon. After the cold war, the government kept it in good condition in case of a new nuclear threat. They loaned it to the black mesa company and performed free maintenance as part of a payment deal (the black mesa company only got 10 billion in government funding a year, according to portal, the facility was added as an extra).
 * Freemans Mind has Gordon mention that the Black Mesa facility contains a lot of old missile silos, so you aren't the only one to consider this.

The ant-lion and leech incursions were manufactured by the combine
Both ant-lions and leeches spread ridiculously fast, taking over large parts of the earth and forcing people into the cities, which made it perfect for the combine invasion. This seems a tad unlikely to be a coincidence. In addition, the portal storms only teleported creatures from Xen, an area featuring neither large bodies of water or any significant room for underground burrows, which are necessary for leeches and ant-lions respectively. It seems more likely that they are part of a standard combine invasion procedure, being teleported in to warm up a planet to a full-scale invasion.

Conquering a planet is a rite-of-passage by the Advisors
Gordan can cause so much damage because the Advisors are actually just children that don't know what the hell they are doing. After their parents mostly conquer a planet, they leave a clutch of their young in pods, known as Shu'ulathoi, to govern things. When things fall apart, the Advisors must hatch, adapt to the non-sterile environment, and take a more direct role. The ones who survive get welcomed back by their parents, the weak are weeded out. In Episode 3, we will see unique advisors each trying diverse and poorly-planned tactics. The G-Man is their babysitter, taking Breen (who was doing too much of the work) out of the picture, and challenging the children.

Aperture Science is the origin of the Combine
In Portal 2, a lot of the insane projects Cave Johnson talks about in his recorded messages sound like they could be the beginnings of the Combine. Experimental cyborg augmentation on hobos, replacing managers with android robots, experimenting with beams that turn blood into gasoline, creating an army of genetically engineered Mantis Men... There are also mentions that Aperture Science was experiencing unexpected time travel in the course of their testing. It seems possible that some component of Aperture Science (i.e. a vessel or outpost like the Borealis) was sent backwards in time and became the seed that eventually turned into the Combine. This is reinforced by the fact that Aperture tech and Combine tech are remarkably similar (even in Portal 2, where the level resources were all entirely original instead of reused from Half Life 2) and both Aperture and the Combine seem characterised by total amorality in the singular pursuit of a focused goal (namely, For Science!!). Building on that, Combine Advisors are simply more advanced, bio-organic versions of Glados,.

The Combine will be destroyed by their own slaves
We know most of the Combine's henchmen are brainwashed or cybernetically altered slaves of theirs. Halflife 3 will involve finiding a way to break the control the Combine have on all their enslaved races all at once, triggering a massive rebellon that takes the Combine down for good.

The G-Man is True Neutral.
He simply exists to move the story in its destined direction, which explains why his loyalties are ambiguous.

Adrian Shepherd and Chell will cameo in Episode 3/Half-Life 3.
It's most likely going to be the last game in the series, so all the characters will come back to say goodbye.

Episode 3/Half-Life 3 will end with Alyx and Gordon marrying.
It's pretty clear the two are shipped in-universe and out-of-universe. Possibly with a Pair the Spares of Chell x Barney or Adrian.

Dr. Breen will die in Episode 3/Half-Life 3 due to Author Existance Failure.
Breen's voice actor died. Valve doesn't seem to be the type to replace VA's. Plus, it's most likely that that game will be the end of the series- the villain needs to die in order to ensure a happy ending.
 * It is debatable whether of not he is already dead. He may have died in the teleporter when it exploded, he may have become an Advisor, or he may be somewhere else.

The Nihilanth is a Great Old One
Come on. He fits every single requirement. Has a race of small versions of him? Check. Utterly creepy? Check. Blue and Orange Morality? Check. Psychic powers? Check. From another dimension? Check. Worshipped as god by other races? Check. Looks like Gordon Freeman really did punch out Cthulhu.

The Zombine's head is still there, but falls off with the headcrab
If you shoot off a Zombine's headcrab, you'll notice that most of the head above the lower jaw is missing. However, you'll also notice that it's trying to contact it's allies before you kill it, despite it's lack of a mouth or even a brain. So, obviously, Zombine's still have their heads when the headcrabs are on, but for whatever reason it comes off when the headcrab dies/detaches.
 * It's possible that the reason the Zombines keep trying to radio their allies is because the headcrab can't subsume the mechanical parts of their brain, which is why they have a jerky movement torn between soldiery things (radioing, pulling grenades) and zombie things (charging the player down with the grenade). The grenade thing could even be the soldier trying to trick the headcrab into a suicide rush to escape the And I Must Scream existence. This actually doesn't affect your WMG much...

There is more than one Overwatch
Overwatch from HL2 sounds much more humanlike than the one in Episode 2. Since the Combine never do anything efficiently if they can make it as cruel and wasteful as possible, clearly the City 17 Overwatch is a human woman strapped into some bloody mess of wires and conductive goop. The vibe comes across if you listen to her announcements: there are some pauses where she sounds a bit like she's trying to avoid saying some things, or find less hurtful ways to think about what she's ordering the troops to do, battling the computer that's forcing her to output certain instructions. In Episode 1, the computer is presumably broken and she's panicking as she's obviously about to die. In Episode 2, City 17 Overwatch is most definitely dead, and the Combine have switched over to an AI-based system now that they're actually fighting on closer-to-equal terms and need to just get on with the task.

The G-Man is one of the Combine
He caused the Black Mesa Incident because there wasn't a big enough portal from their home world, and got Gordon to defeat the Nihlanth to move it out of the Combine's way. Dr. Breen establishes a deal with the Combine and becomes ruler of the earth. When the Combine realizes that Dr. Breen is getting in their way of domination, they ask the G-Man to wake up Gordon, knowing full well what he's capable of. Dr. Breen is killed at the cost of their Citadel Core, and the G-Man puts Gordon back into Stasis until he is needed again. Unfortunately for the G-Man, the Vortiguants interfere and Gordon escapes. The Combine then realizes that Eli Vance, the leader of the resistance, is planning to destroy the Portal. Since Gordon won't kill Eli himself, the G-Man decides to ask a trio of Advisors to kill Eli. Without Eli, the resistance falls apart. The G-Man, meanwhile, happily reports that Eli is out of his way, but somberly reports that the Portal has been destroyed. This leads to another theory of mine...
 * If the Combine wanted Doctor Breen dead they'd just kill him. The scenario you suggest seems overly convoluted and counterintuitive. The Combine would have a lot to lose and very little to gain.

The G-Man will be the final boss of Episode 3
See above theory for context. The G-Man is then told to get rid of Gordon, as he's played his part. The G-Man confronts Gordon and a Boss Battle commences.
 * Considering the only way Gordon could even hope to fight the GMan would be with help from the Vortigaunts, which would necessitate another Gordon/Vortigaunt team-up, then this must happen.

Dr. Kleiner is trying to grow a Gonarch
Gonarch is the hive queen of the headcrabs. A Gonarch would be called a "she" (despite being genderless) which is also a pronoun that Kleiner calls Lamarr. He plans to use Lamarr to end the enslavement of the headcrabs by the Columbine. The plan is to make every zombie and headcrab an allies similar to Vortigaunts.

The legend of Gordon Freeman continued long after Black Mesa.
Gordon's reputation perpetuating and growing to the point where the Combine would direct all of their available forces against him and the Resistance would follow him without question is an essential part of the GMan's plan. However, as one fanfiction notes, despite his amazing feats very few people would care about the actions of a random scientist running around a government facility almost twenty years ago (except the Vortigaunts, but they are a special case). Therefore, the GMan (with some help from Eli, who could have known the bare details of the plan and in any case wanted to keep some hope alive) ensured that tales would be told of Gordon's feats after Black Mesa, spreading rumours implicating him in nearly every single Combine setback or defeat, as well as causing a few himself to lend credence to the idea Gordon was still around, running about and generally ruining the Combine's fun. Thus it's no wonder none of the Resistance questions where Gordon has been all this time, "knowing" he has spent the time harassing the Combine and assume that now he's revealed himself he's ready to destroy them for good, and it's no surprise the Combine send so many of their forces to pursue him after Breen sees him, because finally he reveals himself and they can strike back at the person who has caused them so much trouble.

Grigori is, or will be, in the employ of The Gman.
Basically, The Gman takes an interest in all the badass soldiers of the Half Life Universe: Gordon, Barney, Shephard, Eli, that random Vortigaunt you meet that charges your suit. Grigori has been single handedly taming Ravenholm since its fall, without the help of an HEV suit or any formal arms training. He also helps Gordon, the Gmans only known active employee, get through Ravenholm, something he couldn't have done without Grigoris help.

The reason Episode 3 is taking so long is because it features the portal gun and it is hard to make a game in such a way where the portals won't be a gamebreaker.
Look at the various youtube videos of the portal gun imported into HL2 and the episodes. It makes the game ridiculously easy. So it's taking so long because at one point of Ep.3 Gordon is able to get a ASHPD, and every level past that point has to be made "portal-proofed" so that Gordon doesn't just use the portals to cut a swath of destruction against the Combine like some sort of trickster god.
 * Couldn't they just only have portal surfaces where they were necessary?

Father Grigori was already dead when you found him in Ravenholm.
Like the rest of the citizens, he actually did not manage to survive the headcrabs. However, he did manage to rescue a lot of his neighbors from being headcrab zombies before he died. At one point, he was killed in the battle, but he felt that he needed to save everyone, so his spirit continued living. The Father Grigori you see is just his spirit.

Alternatively, the reason Episode 3/Half-Life 3 is taking so long is that Valve is perfecting the Source engine.
Let's see now: Averting No Flow in CGI for Left 4 Dead, advancing facial animations in Portal2, improved mapping in Team Fortress 2... Valve has something epic lined up.
 * ...facial animations? What?
 * I think he's talking about Wheatley and the rest of the personality cores showing a lot of facial expressions despite technically not having faces at all.

The G-Man provided Gordon with his power.
And that power is the power to save and reload. In general, a Half-Life player will die so much that the odds that Gordon would actually make it seem very low. But every time Gordon fails, he simply rewinds to a few seconds earlier, and retries. G-Man might also have made Gordon mute so that he could not tell anyone else about this.

Gordon was the one who ate all the donuts.
And he doesn't talk so they don't smell his donut breath (or his mouth is still full of donuts).

The reason Gordon can carry all of those weapons? His suit absorbs them and the ammo.
That's why his HUD has the feature to scroll through weapons. He can scroll through them, pick the one he wants/needs, and have it appear in his hand.

Half-life 2 originally was not designed as a sequel to half-life.
Originally, it was a seperate game with Alyx Vance as the main character. This is why the story has so little to do with the original events of half-life. The in-game events require minimal changes (only that Alyx was the one who mis-teleported) between both versions. Head-crabs were originally sackticks and an unnamed synth (http://half-life.wikia.com/wiki/Unidentified_cut_Synth ), while barnacles were simply added to the levels.

Gordon will get to use the portal gun.
The Borealis will contain the Aperture Science Handheld Portal Device and navigating the vessel will require the application of puzzle-solving skills similar to Portal, utilizing the portal gun.

The G-Man is not malevolent at all.
He is just extremely socially awkward. He's not trying to be Gordon's friend or anything like that, he's just trying to deliver him straight information. He just has such bad social skills that he can't do it without sounding really creepy. The times when he seems malevolent, such as putting Gordon into a "battle he has no chance of winning" if he doesn't work for him is just a combination of immaturity, being unable to empathize with anyone, and world-changing powers.

Dr. Breen was (before Half-Life 2) the G-Man's employer.
Dr. Breen had the G-Man get the specific crystal sample that would create the resonance cascade, in order to open a portal with the Combine and quickly strike a deal with them, but first somebody would have to do something about the Nihilanth. Gordon comes in (probably because of the G-Man)... but apparently, killing the Nihilanth was not part of his plan, and so the G-Man was let go. The G-Man seeks out revenge by siding with the resistance years later, possibly under the employment of Eli Vance (or perhaps Eli was forced to work cooperatively with him, being indebted by the rescue of his daughter), and releasing Gordon unto the world, knowing full well what would happen. After the events of episode 1, the G-Man attempts to jostle Eli into allowing them to use the Borealis in order to defeat the Combine by sending a message through Alyx. Eli decides that enough is enough, and so because he is no longer useful to the G-Man's cause.

The baby picture in Gordon Freeman's locker in Half-Life 1 is baby Alyx.
Gordon traveled through time and learned that he would end up with her. There's nothing creepy about him having the picture there - he';s just got a picture of his future wife.

Children of Men takes place in the Half Life universe, between 1 & 2.
Crapsack world? Check. No reproduction? Check. Only thing we're missing is the Combine - maybe they're avoiding England.

Half-Life 3 will have three seperate storylines.
The game begins with a short tutorial level in White Forest as a second Combine army attacks. Gordon flees, aiding the Resistance in pushing back the attack. Eventually, he is wounded and captured by one of three groups that signify the three split storylines.

The Resistance storyline follows Gordon returning to City 17 with the Resistance to defeat the remnants of the Combine, only to discover they are leaving Europe and heading to the Arctic. Gordon follows them there, activating an ancient warp gate using salvaged fuel rods from the remains of the Chernobyl reactor, and rescues Dr. Kleiner and Mossman from the Resistance's base there. Gordon then infiltrates the Borealis, discovering an ancient power source hidden on it, which is taken by the Combine to an ancient underground temple. Gordon enters the temple and destroys the Consul, the supreme leader of the Combine, winning the war.

The Combine storyline begins with Gordon captured by the Combine in the Arctic, a prisoner of Dr. Breen, whose injured body has been merged with an advisor. Gordon escapes, but is targeted by his fellow Resistance members for capture, due to rumors of him being mind-controlled. Gordon is eventually forced to do the Combine's bidding by fighting the Resistance and retrieving the power source from the Borealis. Eventually, he journeys back to City 17 and fights the ancient dark being hidden in the power source, allowing the Combine to take over.

The Benefactors storyline begins in Chernobyl, with Gordon a prisoner of the G-Man and his mind-controlled superhuman slave, Adrian Shephard. As Gordon is forced to fight against the Resistance and Combine in City 17 and the Arctic, he learns that G-Man is the embassador for an interdimensional species whom plan to use the power source hidden on the Borealis to heal their shattered world. Eventually, G-Man betrays Gordon by leaving him to die, forcing Gordon to pursue and defeat him. Gordon kills the G-Man, but the power source is activated, effectively destroying all human life on Earth and rendering Gordon the sole survivor of his species.

Gordon has a superpower without knowing it.
A quote from vortigaunts in Half-Life 2 says "Your mind is opaque." This means that Gordon has a passive ability that he most likely is not even aware of; his mind is resistant to telepathy and probing. This is the reason G-Man is using him against the Combine - the Advisors have Psychic Powers, so somebody with an "opaque mind" was needed to combat them.

Headcrabs prefer to couple with very intelligent brains
Which is why only scientists got zombified in the original Half-Life, because they went after the genius scientist brains.

Odessa Cubbage is secretly a Special Air Service operative.
He looks like a security guard. He seems incompetent. He seems almost cowardly... But it's all a ruse. Perhaps he actually DID bring down a helicopter over New Little Odessa, just after Gordon did. That security guard garb is just to draw attention from the sand-coloured beret on his head. 'What sand-coloured beret?' I hear you ask. 'I never saw a sand-coloured beret!' Exactly...

The G-Man's employers are native to Xen
So the G-man and his superiors were living their lives in the borderworld, occasionally getting vistors from other worlds experimenting with teleportation technology, but all in all, it's a rather peaceful existence. Then suddenly, the Nihilanth decides to set up camp in Xen to escape the Combine. The G-man and his employers believe that the Combine may attept to attack Xen, and such an conflict may not only cause serious collateral damage to their home, but may cause the Combine to discover and enslave them as well. So they send one of their own to Earth to set up the Resonance Cascade, hoping their unwanted guests will invade Earth. Gordon defeats the Nihilanth, and Xen is once more their domain, hence "The borderworld, Xen, is in our control, for the time being.." . But, the Combine invade Earth, something that wasn't part of the plan. Guilty for causing the enslavement of a race that never caused them any real harm, the G-man is instructed to assist humanity with defeating the Combine.

Now I know what you're thinking, if the G-man's employers live in Xen, where were they? You did see them, you killed a few. The G-man and his employee's are the Xen crystals, at least, the physical parts of them are. The crystal the G-man "gave" to Black Mesa, that caused the Resonance Cascade, that was his phsyical self.