Half-Life 2



""The Right Man in the Wrong Place can make all the difference... in the world. So... wake up Mr. Freeman. Wake up and smell the ashes.""

- The G-Man

In 2004, Valve released the sequel to their revolutionary and critically acclaimed first game Half-Life, Half-Life 2, which itself broke new ground on many fronts in its graphics engine, physics system, and its online distribution/updating system.

Half-Life 2 starts off about twenty years after the ending of the original game, as the mysterious G-Man uses his time and space bending powers to place Gordon Freeman on a train headed for City 17, some undisclosed place in Eastern-Europe. Gordon soon finds out that Earth has been invaded and conquered by a powerful alien force known as the Combine, which apparently detected the Black Mesa incident and took advantage of it to enslave humanity and add Earth to its collection of assimilated worlds. Having attained an almost messianic status among the fledgling resistance forces thanks to his actions in Black Mesa, Gordon's attempts to survive and eventually strike back against the Combine provoke a full-scale revolution. In this, he is aided by the Vortigaunts, an alien race whose enslavement he broke by his destruction of the Nihilanth; members of the Resistance, including several former Black Mesa scientists; and Action Girl Alyx Vance, who accompanies Freeman throughout much of the game as a fully-qualified AI partner. He is opposed by the vile Dr. Breen, former administrator of Black Mesa and now self-styled overlord of humanity.

The game was followed by even more sequels, called "Episodes", supposed to cut down on the development time that a full sequel would take, by releasing shorter games more frequently. The Episodes chronicle Alyx and Gordon's escape from City 17, and the rebels' continuous struggle against the remaining Combine forces, who are seemingly controlled by the mysterious "Advisors". Episode One was released in 2006, and Episode Two was released in 2007 alongside Portal and Team Fortress 2 in The Orange Box. As of 2012, any details about Episode Three, besides that it will be the last chapter in the Episodes trilogy and bring an end to the Story Arc started by Half-Life 2, are minimal, and no release date is announced.

Half-Life 2 contains examples of:
"Alyx: "Man of few words, aren't you?"
 * Abandoned Hospital: One of the settings in Episode One, which appears to have been taken over by the Combine and, from the looks of things, is in the process of being abandoned again.
 * Abandoned Mine: In Episode 2, one of these holds an antlion nest and a rebel outpost.
 * Abnormal Ammo: The crossbow in Half-Life 2 shoots red-hot metal bars normally used to reinforce concrete.
 * Any object picked up with the gravity gun can be launched as a lethal projectile as well, such as circular saw blades in Ravenholm.
 * The Abridged Series: Half Life 2 in 60 Seconds.
 * ~AcCENT Upon The Wrong SylLABle~: The G-Man speaks with this.
 * Part of this is down to the fact the G-Man is not human at all, merely using a human host body or projection. The most blatant case of this is abetted by the fact that Gordon's temporal rate is being tweaked back out of slow-time suspension while G-Man is speaking to him.
 * Action Girl: Alyx Vance
 * Advancing Wall of Doom: The articulated, sectional wall near the escape from Nova Prospekt.
 * After the End: From Half-Life 2 on, the setting is post-apocalyptic, devastated by multiple alien invasions.
 * Air Vent Passageway: Alyx lampshades it quite gleefully in Episode One.
 * All Animals Are Dogs: DOG himself, whose morphology is (at least by now, after all the modification Alyx has been doing to him) much closer to that of a great ape, but still retains the doglike behavior he had programmed into him.
 * And I Must Scream: It is implied in-game that headcrab zombies are fully conscious and aware of their situation. Also, if you play their audio backwards, it becomes rather... disturbing.
 * Artificial Brilliance: Half-Life 2 often appears to have bad AI - enemies that just stand there shooting at you. However, the AI is actually pretty good - it's the level design which often doesn't make the most of it. HL2 soldiers are programmed to take cover and look after one another, but in the tight corridors that a lot of the game takes place in, this can't be well demonstrated. This video demonstrates the AI in action.
 * Hunters are even better when it comes to the AI department - they suspiciously often take pathfinding decisions that result in at least one of the Hunters in the pack ending up ahead of a fleeing prey, cutting off the escape route. And if you try running them over with your vehicle, they'll act as though they're about to be hit, and then jump to the side at the last minute.
 * Artificial Stupidity: Resistance fighters in Half-Life 2 are actually pretty good A.I.-wise (they strafe/use cover, verbally recognize different enemy types (i.e. "Combine!" "Zombies!"), and are smart enough to back away from melee enemies while firing), but they do have an annoying tendency to charge straight into sniper rifle fire, cluster around the player instead of giving Gordon some breathing space, and cannot be told to "wait" in a safe position for more than several seconds.
 * There is also the infamous "barrel trick" in Half Life 2, where a certain Metrocop gunner in the beginning of the Water Hazard chapter can't see you if you can't see him (say, if you carry a barrel or even a paint can so that it obstructs your view of him). (For example, here).
 * Ascended Extra: Barney Calhoun, Isaac Kleiner and Eli Vance.
 * Ascended Glitch: As the developer's notes will tell you, a glitch that worked for the best and was thus never removed provided the most empathetic moment for DOG
 * Badass Preacher: Father Grigori.
 * Whether or not Grigori is actually an ordained priest was intentionally left ambiguous: he's one hundred percent Laughing Mad and states that he used to be a mechanic. Thankfully this doesn't detract from his badass status.
 * The Beast Master: Gordon Freeman is a type 2 once he gets
 * Bittersweet Ending: Episode Two.
 * Blinding Camera Flash: The scanner enemies do this if you're looking at them when they photograph you (this is pretty much the only hazard they pose, apart from occasionally giving your position away to a strider).
 * Revisited in a much deadlier fashion in the Episodes as the Advisors' mental attack is displayed onscreen as a visual distortion, including the Bittersweet Ending above.
 * Border Patrol: Leeches will attack if you wander too far into the sea, and unlike the first game they're unkillable.
 * Bullfight Boss: The Antlion Guards.
 * But Not Too Black: With a black father and a Malaysian mother, Alyx is at best Ambiguously Brown herself. Gets particularly jarring if one looks at a picture of Jamil Mullen (whose likeness Alyx was modeled on), who could credibly pass for Eli's daughter. Presumably Alyx really takes after her mother.
 * Given the existence of Quincey Jones' real life daughter Rashida Jones (and knowledge of the many ways interracial genetics can manifest) Alyx's appearance becomes significantly less jarring.
 * Iron Butt Monkey: Alyx Vance, while not for comedic purposes, is an Iron Buttmonkey of Kenny proportions. For the first years of her life, she lives in the dormitories of Black Mesa, a sweltering hot research facility. Then, her during the Resonance Cascade incident. She only survives because   saves her life, putting her in a debt that she repays in Episode Two. Fast forward to when she meets Gordon Freeman. She is then separated from him by a malfunctioning teleporter, forcing Gordon to  . Her father is then   and the rest of the game is mostly spent trying to rescue him. In the end, when the, she only . In Episode One, the  . In the beginning of Episode Two, she is   Finally, after
 * Calling Shotgun: Alyx, before she and Gordon Freeman go for a ride in a car.
 * The Can Kicked Him: There's an achievement in Half-Life 2 for killing an enemy with a toilet.
 * Captain Ersatz: Antlions = The Bugs from Starship Troopers. And Advisors = Guild Navigators.
 * Car Fu: Thanks to the Havok physics engine and the Gravity Gun, cars are deadly weapons. The driving sequences in Half-Life 2 and Episode 2 both feature ramming as instant-kills on most enemies, and the Gravity Gun can punt abandoned cars for major damage. There's also a sequence where you can use a magnetic crane to smash Combine soldiers with the car. The Antlion Guardians get revenge, though; their AI in Episodes 1 and 2 is programmed to deliberately heave cars at you.
 * Since you use cars to plug their emergence holes in Episode One, it could just be Car Fu Escalation all around.
 * Catch and Return: You can do this with the Gravity Gun, naturally. Technically you can pick up and throw armed grenades by hand, too, but not quite as far.
 * Much like Flushed, the Achievement for killing something with a toilet in the main game, Episode One has an achievement for killing a Zombine with its own grenade.
 * Childless Dystopia: The whole world due to the suppression field.
 * The Computer Is a Cheating Bastard: Inverted. There is a weapon called the AR2 pulse rifle that is the standard issue firearm for the Combine's Elite Mooks and a somewhat common infantry weapon employed by standard overwatch soldiers. The AR2 has good accuracy, a fast reload time, and two fire modes: Primary fire fires the gun itself (which is fully automatic and does eight damage, requiring seven shots to drop a standard Combine soldier). Secondary fire is a dark energy ball that can kill anything smaller than an APC in one hit. Presumably because of the HEV suit's military-grade armour plating, that AR2's primary fire is coded only to do three damage to the player (same as the more common MP7) instead of the usual eight, and the secondary fire only does fifteen points of damage rather than being an instant kill. However, on hard, it does deal a lot more damage than the regular MP7. You do not want to get one of those secondary-fire orbs on you in the middle of a gunfight...
 * Cool Boat: A fan driven boat that can run on land. Mounted with an infinite ammo gun that was ripped off an attack helicopter.
 * The Mudskipper is specifically equipped with it to take down the one(s) thatcaused such grief during the earlier parts of Water Hazard. As the Railroad Rebel says, "I like to bring a little irony to a firefight." If you don't monkey with it, the recharge and firing periods are the same as the hunter chopper, but you do a lot more damage to things with it than is done to you, just as with the AR 2 in the above listing.
 * Cool Car: Muscle Car. Then there's the original car, which is an extremely fast dune buggy with nitrous oxide tanks and a laser Tau Particle Gun on top.
 * Crapsack World: Earth in the hands of the Combine; overrun with such otherworldly horrors as antlions, headcrabs, & barnacles, what few cities that remain are barely-functioning ruins, and humans seem to be on the brink of extinction.
 * Crazy Survivalist: The questionably sane Father Grigori.
 * Crouching Moron, Hidden Badass: Aww, see DOG follow Alyx like a sweet puppy. See DOG play catch with Gordon. See DOG hurl himself onto a strider, punch through its chassis, and rip its goddamned brains out.
 * Gordon himself. Before the whole mess started at Black Mesa, he was a valued but decidedly junior theoretical physicist with an interest in athletics, often picked to do the grunt work as he was talented with a HEV suit. (This is lampshaded in Red Letter Day by Barney early on in HL 2.) From then on, he proves himself to be a Determinator, chewing through anything that gets in the way and being noted for how unlikely his survival talents are by everyone from the G-Man to Breen.
 * Cute Machines: Dog.
 * Cyber Cyclops: The Elite Combine in white armor have one, glowing red eye.
 * Degraded Boss: The Striders get significantly easier to destroy as you move through the games. Justified somewhat in that you're getting better weapons to deal with them. Completely averted in Episode One, where a Strider is not only the final boss, but easily one of the most frustrating things to fight in the entire series thanks to its near-perfect aim.
 * In Episode Two, the Antlion Guardian, inside the tunnels, is ridiculously dangerous, being as tough as a regular guard and covered in a very potent neurotoxin. But when you actually have to kill it, the neurotoxin power has been removed, essentially turning it into a palette-swapped Guard.
 * Desolation Shot: Used extensively in Episode One and Episode Two.
 * Deus Exit Machina: The developers had to contrive many ways to keep DOG directed away from the player. He shows in his crowning moments just how big a Game Breaker he'd be if he stayed with Gordon and Alyx.
 * Dual Boss: The first boss fight in Episode 2 is a fight against a pair of Antlion Guards (technically a Guard and a Guardian, which is just a palette swapped Guard) and their normal antlions minions. They don't hesitate to attack you at the same time, but you've got a healthy supply of SMG and Shotgun ammo, a safe spot were they can't strike you, and several exploding barrels lying around the valley...
 * DVD Commentary: In Episode One and Two and the spinoff Lost Coast, there are commentary bubble icons the player can "use" to listen to information about making the games.
 * Eleventh-Hour Superpower: Your Gravity Gun gets a massive upgrade and allows you to pretty much pwn your way into the heavily guarded Citadel.
 * This returns for the beginning of Episode One.
 * The Empire: The Combine are a clear example. Their plans for Earth? 1) Invade; this includes most humans dying. 2) Remaining population becomes either a Stalker, a Transhuman soldier, or dead. 3) Resources, including oceans and atmosphere, get transferred off-planet.
 * Episodic Game: Valve decided to continue the story of Half Life 2 in episodes, when the concept was new (And it still is a fairly recent one) However; it turned out to be averted, since the point of Episodic Gameplay is to not keep people waiting for a long while in between episodes. Episode two was criticised for this by Zero Punctuation, but a lot of people shrugged it off because it was at least released as part of a bundle. Episode Three, as of 2012, appears to still be in development. That's right...it's been in development for more than four years. (And was already in development while they developed Episode Two, as said in the commentary node for the gunship battle) It's almost been jokingly called "Valve's Duke Nukem Forever".
 * Valve themselves seem to agree: Episode 3's release date is currently listed as "Coincident with The Rapture".
 * Face Heel Turn:.
 * Flechette Storm: In Episode 2, the Hunters have an automatic cannon that launches explosive flechettes as their main weapon, and they often come in packs, so having several Hunters shoot at you at the same time creates this effect.
 * Friendly Fireproof
 * Force Field Door
 * Foreboding Architecture: The Citadel, Nova Prospekt, the abandoned Cold War era rocket facilities.
 * Foreshadowing: "That's the old passage to Ravenholm...we don't go there anymore." Guess where you're headed?
 * Also in the comment that it is spawning season for the Antlions. Very possibly in G-Man's warning to Eli (by way of his daughter) to prepare. White Forest's successful shutdown of the superportal, after all.
 * Gaia's Lament: Earth in Half-Life 2, which has been ravaged and drained of its resources. Water especially. Check out the designs of all the levels that feature waterways or oceans, there's plenty of clues in the scenery that the water level used to be about 5 metres higher than it is now. The amount of water that's been stolen to make global water levels drop that much is truly mind-boggling.
 * Give Geeks a Chance: Alyx certainly seems willing to, but admittedly Gordon is a pretty badass geek, to the point that he renders her almost speechless taking down a Gunship singlehandedly in Episode One.
 * Goddamn Bats: The commentary for the episodes notes that black headcrabs were found to be perfect for scaring the player, without actually being a threat, as they will bring Gordon's HP to One, but can't kill him and his HP is restored to what it was before rather quickly.
 * Go Look At the Distraction: Eli sending Alyx to make tea so he can tell Gordon about the G-Man.
 * Gravity Barrier: Literally. Combine Civil Protection set up odd forcefields to block citizens from entering certain areas.
 * Hair Decorations: Doctor Judith Mossman has a large plain hair clip at the back of her head.
 * Heroic Mime: Lampshaded repeatedly in the second game.

"Leave the talking to me, Gordon.""

"Vortigaunt: How many are there in you? Whose hopes and dreams do you encompass?"
 * Hide Your Children: Justified; the Combine have been suppressing reproduction for almost 20 years by the time of HL2.
 * Hollywood Tactics: The Combine suffer a huge dose of this in one battle in Half Life 2. When word first reaches them that Gordon has come back, they mobilize hundreds of Civil Protection officers, Armored Personnel Carriers, and Hunter-Choppers to go after him. They're all slaughtered. Then Gordon survives through Ravenholm and starts wiping out several Combine Overwatch checkpoints along the coast. The Combine then got solid intel somehow about his location at Lighthouse Point. So what do they do? Send a bunch of planes to drop lots of bombs from the safety of the air, where he can't touch them? Nope. Instead they send a Synth gunship and several squads of troops. Can you guess what happens next?
 * Holy Hitman: Father Grigori.
 * Huge Holographic Head: Breencasts.
 * Iconic Weapon: The Crowbar. In HL 2, it's the weapon Barney gives you before you make your run for the canals (and implied to be the same one Gordon dropped in Black Mesa).
 * In Episode 1, he gives you another and lampshades that he's starting to run low on them, and Alyx mentions it in reference to a victory he just achieved.
 * In Episode Two, the G-Man cites its attack as what the Vortigaunts knew of humanity before Gordon freed them by killing the Nihilanth.
 * Icon of Rebellion:
 * Gordon Freeman, who certainly becomes a Messiah-type figure to the ragtag human rebellion in City 17, and the Lambda symbol itself becomes a common symbol to denote rebels and the caches they hide around the city and surrounding countryside.
 * Also Father Grigori's shoes. Red sneakers were a fashion taken up by freedom-loving Eastern Europeans during the glasnost era, and Father Grigori looks to have been one of those rakish youths back in the day...
 * Improvised Weapon: The Gravity Gun, which turns virtually anything into a weapon: Chairs, crates, tables, barrels (exploding and non-exploding varieties), benches, radiators, armoires, TVs, tires, bicycles, cars, people...
 * Incredibly Lame Pun: "Zombine, get it?" Admit it, you laughed.
 * Instant Cooldown: Subverted with the Combine's Dark Energy reactor.
 * Invisible Wall: There are invisible walls over the tops of fences in certain areas so that the player cannot stack crates to go over them.
 * Involuntary Group Split:
 * Happens at the end of Black Mesa East, when the Combine shells the hideout and causes a cave-in.
 * Recurs during Anticitizen One, when Dog opens a Combine barrier then is carried off by a troop transport, then again when Alyx later scales a building to spot the means for much less monkey-like Gordon to progress by and is promptly captured by a Combine patrol.
 * It's Probably Nothing: The people worry about the mind-controlling water in HL2, but have no choice (unless they live outside the city, in which case they can just throw together a purifier). One of the scientists uses this exact phrase just before the experiment at the beginning of the first game. Yeah, that one that tears a hole in reality and causes all hell to break loose.
 * I Want Grandkids: Eli mentions this to Alyx while winking at Gordon.
 * Lampshade Hanging: A quarter of the Vortigaunt's lines in Episode 2 are poking fun at the game's own use of tropes, such as the prevalence of Broken Bridges or Gordon's habit of falling into pits. Examples include, "Pity the generator that requires a Vortigaunt to operate," "No pit would be complete without a Freeman climbing out of it," and, "What next in the parade of constant obstacles?"
 * Laser Sight: The Combine Snipers, the Rocket Launcher, and the Combine Autogun in Episode Two.
 * How did we not even mention the rocket launcher, which guides the missle after it is launched with the laser sight?
 * Leaning on the Fourth Wall: The Vortigaunts tend to do this, if you stick around and listen to them enough. In Episode 2, various ones spend a great deal of time remarking on the ridiculous number of convenient obstacles put in Gordon's way. (see the Lampshading entry above for specific examples) Even in Half-Life 2, however, they did a little leaning, mentioning "the eyes within your own, the minds within your mind". In context, it seems to refer to but it also seems to be the Vortigaunts subtly pointing out that Gordon is and has been controlled by thousands of different players.


 * Lightning Bruiser:
 * Hunters are crazy fast and crazy tough (able to eat almost 2 mags of automatic weapons fire before dying), and have a pretty mean automatic cannon for a nose. Antlion Guards are also fast and tough, but their dependence on melee ramming makes them more of a Bullfight Boss.
 * The Hunter Choppers, who instead of being Heavies like the Hunters or Boss in Mook Clothing like the Guards, are straight bosses themselves. They are far superior to any other vehicle or Synth the combine can field. They fly, move extremely fast, can eat up much more damage than an APC, and come armed with an unerringly accurate and powerful pulse machine gun and a seemingly unlimited supply of mines. Fortunately, they're rare (only two are encountered in the whole series thus far) and you're fortunate enough to encounter while they're on their own and you've already killed all mooks prior to fighting them.
 * Malevolent Architecture: Combine architecture is designed to slowly expand and consume anything that gets in its way.
 * Master of Unlocking: Alyx.
 * Mecha-Mooks
 * The Messiah: The Vortigaunts revere Gordon Freeman as a Messianic Figure after he lead to them being freed from generations of slavery in Half Life. To them, he is "The Free Man".
 * Meta Guy: The All Knowing Vortigaunt.
 * Mind Over Matter: The Combine Advisors have telekinetic powers, enough to crush metal barrels, snap a human spine, or hold you in place for the game's equivalent of cutscenes.
 * Misanthrope Supreme: Dr. Breen.
 * No Arc in Archery: Averted, at least in Half-Life 2. When using the crossbow at long range, the player must compensate for arrow drop.
 * Also averted with the Gravity Gun.
 * No Fair Cheating: Early on in the game, when you are walking through the square without any weapons, a Strider walks past in the distance, behind a roadblock. If you put the cheat codes in and blast the Strider with the rocket launcher (which you don't normally have at this point in the game) as it passes, it pauses and glares at you for a moment before continuing on its way.
 * No-Holds-Barred Beatdown: The Seven Hour War between all the nations of Earth and the Combine. It lasted seven hours, and... well, we lost.
 * Nonstandard Game Over: The "status report" deaths:

Any time you let die a scientist who is needed to open a locked door or perform an important scripted event.

Letting Alyx or Barney die in any game where they are in combat (which probably will never happen to you anyway).

Losing your vehicle in any of the Half-Life 2 games (especially weird after you aren't being specifically controlled by a status-reporting G-Man anymore).

If you fail in Episode Two, you get a Vortigaunt-styled message, reflecting the fact that the G-Man is no longer controlling you. ("the Magnusson's misgivings about the Freeman were completely justified.") "Resistance Member: When this is all over, I'm gonna mate."
 * No Sex Allowed: Noted early on in HL2 when Breen reads a letter from a concerned citizen about the "Suppression Field" that keeps people from reproducing. Amusingly, later in the game you come across another "Suppression Device": A giant laser cannon. That'll kill the mood alright.

"Alyx: Did Dr. Kleiner just tell everyone to...get busy?"
 * Also, after the Citadel has fallen:

"Female Rebel: What's the password?
 * No Transhumanism Allowed: Despite the fact the technology is available, and the situation desperate enough that cybernetic modification is rather plausible, only the Combine's human loyalists (who are even called the Transhuman Forces) have cybernetic upgrades of any kind... well, them and the Stalkers -- dissident (or just unlucky) humans mutilated into mindless cyborg drones. Even the Combine's "leader of humanity" hasn't upgraded himself, despite talking of his own free will about how the Combine are here to elevate humanity to the next stage. In fact, when the Advisor suggests uploading him into a host body, his initial response is "You must be joking!" Originally, Breen's place was taken by 'the Consul', who rendered himself immortal using the Combine's life support technology.
 * Not Even Bothering with the Accent: City 17 is meant to be in Eastern Europe, yet all your fellow citizens are apparently American.
 * This is half-explained by the fact that City 17 is the largest of a number of "City #" megacities around the globe, and that most of the human population (minus the Resistance, of course) have been ferried around.
 * Once Killed a Man with A Noodle Implement: In Episode 2, a Rebel-in-Training at the White Forest Base (also called the AR3 Guy) first claims to have used AR3s (which don't exist), then claims to have killed Hunters (alien tripod cyborgs that are rather deadly) "with his own hands."
 * Our Zombies Are Different: Zombies are actually living (if gangrenous and mutated) people that have been hijacked by headcrabs. Half-Life 2 introduces Fast and Poison varieties, and Episode 1 depicts what happens when Combine troopers get zombified.
 * Oxygen Meter: It's also grouped together with the flashlight and the sprint meter in Half-Life 2 and Episode One, which makes underwater sequences harder if you didn't have time to recharge.
 * The Password Is Always Swordfish: This exchange in Half-Life 2.

Male Rebel: Password, now open up!"

"(Presumably the same)Female Rebel: What's the password?
 * Later parodied:

(Likewise)Male Rebel: I'm not even going to tell you to shut up."

"Barney: And if you see Dr. Breen, tell him I said f (loud crashing sound) k you! Hahaha!"
 * Pet Monstrosity: Lamarr.
 * Plea of Personal Necessity: When he is about to be spectacularly destroyed, Dr. Breen tells Gordon, "You need me!"
 * POV Boy, Poster Girl: Gordon Freeman and Alyx Vance. Though Gordon is the player character, the two get equal billing on promotional material, including boxart, and it's Alyx's introduction that really kicks off the plot. It's implied that Alyx was the Resistance's top operative until Gordon shows up.
 * Power-Up Magnet: One of the side effects of the Gravity Gun.
 * Precision F-Strike: Barney Calhoun.

"Vortigaunt: ''"The Freeman dispatched the enemies with great dispatch.""
 * Putting on the Reich:
 * The Combine Elites might qualify in some cases for this (e.g. the boots).
 * It seems the developers had this trope in mind even during the earliest conceptual phase.
 * The Quisling: Wallace Breen, who sold out the human race to the Combine.
 * Quote Bin: The All-Knowing Vortigaunt.
 * Ragdoll Physics: An integral part of the Source engine, courtesy of Havok.
 * Railroad Tracks of Doom: You're driving a buggy down a train bridge, a stopped train taking up one of the two tracks. You're halfway across when you suddenly hear a blaring horn...
 * Redundant Department of Redundancy:

"Alyx Vance: Did Dr. Kleiner just tell everyone to...get busy?"
 * Rescue Introduction: Alyx introduces herself by rescuing Gordon.
 * Respawning Enemies: Antlions will respawn forever from the ground or holes in the pavement; in Episode One you are able to plug up the holes by shoving cars onto them with the gravity gun. One of the NPCs even hangs a lampshade on this: "It's spawning season for the antlions!"
 * Roar Before Beating: Fast zombies.
 * This behaviour is actually useful for the player, as it will step back and roar after landing a couple of hits... with the headcrab getting right in your shotgun's crosshairs. BANG.
 * Robot Buddy: DOG
 * Scary Shiny Glasses: The eyes in the masks of Combine Civil Protection and Overwatch troops in Half-Life 2 shine like this. (CP silver, Overwatch blue.)
 * Scenery Porn: Near the end of the "Water Hazard" level, as the sunset paints the hills gold ...
 * Self-Imposed Challenge: Some of the Achievements are this. For example:
 * Half-Life 2 challenges you to beat Ravenholm with only the Gravity Gun.
 * In the Xbox 360 version of Episode One, there is an achievement called "The One Free Bullet." You get one shot to shoot off a padlock and that's the only round you can fire in the game. Feel free to use as many explosives and physics objects as you like, though.
 * Shooting down the helicopter in Episode Two without missing once is also an Achievement.
 * Lets not forget "Little Rocket Man" (carry the gnome you discover at the start of episode two all the way through the game and place him in the rocket, inside a special compartment at the end of the game).
 * Not stepping on the sand in the Half-Life 2 chapter Sandtraps.
 * Saving all citizens in the last chapter of Episode One. Compared to the rest of the challenges, however, this one is fairly easy.
 * Keeping all buildings intact during the strider battle in Episode Two.
 * Shotguns Are Just Better: Even Alyx gets in on the action for part of the game.
 * She lampshades it, too; "We came here to get medical supplies; I got a shotgun!"
 * Shout-Out: Lamarr the Headcrab -- Hedy Lamarr (get it?) was a well-known, glamorous actress between about 1940 and 1960 (and, incidentally, also co-invented an early form of spread-spectrum wireless communications), but she's probably better known for suing Mel Brooks for naming the main villain of Blazing Saddles "Hedley Lamarr." So what if we name a de-fanged brain-devouring parasite after her...
 * Hedy Lamarr is probably known even better for being one of the first women ever that appeared fully naked in a movie (Extase, a Czechoslovak film directed by Gustav Machaty in 1932). Naming a pet headcrab after her can be viewed as way more disturbing than the previous reason.
 * Also, in Episode Two there's a Shout-Out to the original Half-Life by Doctor Magnusson. One of the things you can do just after the Resonance Cascade is return to the break room and investigate the microwave, which has a thoroughly overcooked meal in it, completely ruined when the appliance overloaded. Over twenty years later, Doctor Magnusson still holds a grudge over that casserole..
 * Skeleton Key: Alyx appears to have an electronic one about half-way through Half-Life 2, which opens all doors in Nova Prospekt and can also hack Combine computer consoles.
 * Her EMP hacking device is used in the eleventh-hour Heel Face Turn by  and figures heavily in Alyx's contribution to re-invading and escaping a second time from the Citadel and City 17 in Episode One.
 * Shut UP, Hannibal: Sort of: you can use the Blue Gravity Gun to either rip out or just blast the Breencasts. Except the last one, which Breen does on an unbreakable screen.
 * Slept Through the Apocalypse: Gordon, wake up and smell the ashes.
 * Smug Snake: Dr. Breen, particularly by the end.
 * Snap to the Side: On the cover of Half-Life 2, Gordon and Alyx perform one.
 * Sound Effect Bleep: When you first break into the Citadel, Barney tells you, "And if you see Dr. Breen, tell him I said 'fuSLAMou'!" He is cut off by the sound of the wall segment that Dog was holding up crashing back down. The voice file itself isn't bleeped, however.
 * Spiteful Spit: Done by Alyx to Dr. Breen.
 * Star Scraper: The Citadel.
 * Sterility Plague: The combine have set up some sort of device which makes humans unable to reproduce. In the expansions this has been deactivated, leading to Dr. Kleiner to suggest that repopulation can begin.

"Barney: Is [the teleporter] working? For real this time? Because I still have nightmares about that cat.
 * Steven Ulysses Perhero: Lampshaded; Gordon Freeman is often called "the one Free Man" by the Resistance.
 * Keep in mind that Gordon was originally named for brilliant theoretical physicist Freeman Dyson.
 * Stock Scream: The fast zombies' screech is a slightly modified but still-recognizable form of the Howie Long Scream.
 * Storming the Castle:
 * Surveillance Drone: The city scanners.
 * Suspicious Videogame Generosity: Your protective suit has 100 points of armour when fully charged, and the wall chargers can give you 75 points (on easy). When you make it into the Citadel at the end of the game, the wall charger charges you up to 200 points. Uh-oh.
 * Sweater Girl: Dr Judith Mossman. Concerned pointed this out a couple times.
 * Tactical Suicide Boss: The Hunter Chopper encountered in Episode 2 can only be killed by throwing its mines back at it with the gravity gun, since it's Immune to Bullets and you lack explosives.
 * Talking to Himself: There is only one voice actor each for all male and female rebels. Any time two same-sex rebels have a conversation, it's with the same voice. Episode Two added a second voice actor for Sheckley since he was specifically written to converse with Griggs (who is voiced by the same guy as the other male rebels).
 * Done in-game during Point Insertion, as one man paces in front of the arrival/departure board repeating worries about the trains and disappearances. It's quite clear he's not talking to anybody but himself.
 * Tear Your Face Off: The headcrab zombies can be seen to have had their face eaten away (and what's left of it set in a scream) if you shoot off the headcrab.
 * Teleporter Accident:
 * Presumably what happened to the cat Dr. Kleiner used to test the teleporter. Alyx hasn't heard about it until Barney mentions it in-game.

Dr. Kleiner: Now, now, there's nothing to be worried about.

Alyx: What cat?

Dr. Kleiner: We've made major strides since then. Major strides.

Alyx: What cat?"


 * After hooking back up with Barney during the rebellion, he has a flashback about it. Whatever happened, it must have been traumatic, as he was plainly traumatized.
 * Doing this to Kleiner's mini-teleporter is an achievement named "What cat?".
 * Ten-Second Flashlight: Played straight, where it shared the same energy meter as sprinting and holding your breath. In the original game the flashlight had its own meter, and it was given one again in Episode Two. In the latter case, the light recharges pretty quickly, but it takes ages for them to run out.
 * Tentative Light: The flares in Episode One will do this before going out. In Episode Two, your flashlight will blink before turning off; it's much easier to get it back on than before, though.
 * There Is No Kill Like Overkill: Hinted at by Dr. Breen in the Combine Teleporter. "You, on the other hand, will be destroyed in every way it is possible to be destroyed, and in some ways which are essentially impossible!"
 * Those Two Guys:
 * Griggs and Sheckley in Episode Two.
 * The couple from HL2 have shown up twice in the game (once before the apartment raid, the second after the uprising), and once in both episodes.
 * Training Dummy: The disabled Strider at the end of Episode Two, as well as a dead Combine soldier tied to a post after you get the pheropods in Half-Life 2.
 * Triang Relations: Alyx Vance, Eli Vance and Judith Mossman are an example of Type 7a. Alyx loves her father Eli, but does not get on with Judith. Eli and Judith, however, seem to feel something more than professional respect for each other.
 * Trigger Phrase:
 * Tripod Terror: Striders and Hunters.
 * Trojan Prisoner: Employed in the beginning. Barney, as an undercover Civil Protection officer, takes Gordon in for "interrogation" and helps him escape.
 * Uncanny Valley: Averted in Half-Life 2, thanks to some damn fine graphics, motion capture, and animation - except deliberately invoked in the G-Man's case. The subtle asymmetries of his face, some odd mannerisms, the ways he speaks, as though he knows how to make the sounds of speech but isn't sure how they all fit together... all help make him a very creepy supernatural stalker.
 * Underground Railroad: A network of safehouses that guide citizens hoping to escape from City 17. When the Combine bring the hammer down trying to stop Gordon Freeman from escaping, much of the railroad ends up being destroyed helping him get away.
 * The Usual Adversaries: The Combine.
 * The Very Definitely Final Dungeon: The Citadel in Half-Life 2.
 * Vichy Earth: After the Seven Hour War, the whole planet is under the control of the Combine with a puppet regime with Breen as president.
 * Video Phone: The sequel features several Video Phone calls, notably between Alyx and her father. Extra points for touching the screen to emphasize the separation.
 * Villainous Breakdown: Doctor Breen's broadcasts show him growing increasingly short-tempered, until he finally snaps and begins haranguing Gordon directly.
 * Coming to a logical conclusion after he realises you're right on his tail.
 * Water Source Tampering: A man on the first level tells you not to drink the bottled water in City 17 because "they put something in it to make you forget".
 * Wham! Episode: Half-Life 2: Episode 2, we find out that, Aperture Science may have a big part, and.
 * Wreaking Havok
 * In more than one way. Gordon's ability to throw a wrench into the works was why he was pulled out of stasis by the G-Man in the first place. Also, the Havok engine variant Source was developed for the game.
 * Wrench Wench: Alyx knows advanced engineering and interdimensional physics the way somebody raised by a mechanic knows cars. (Which she also knows.)
 * She also knows helicopters.
 * Year Outside, Hour Inside:
 * Gordon's stasis apparently seemed like a day to him, but two decades pass.
 * Also, when Alyx and Gordon go through the teleporter near the end of Half-Life 2, a week passes in what is to them a blink of the eye.
 * Gordon's rescue from going back into stasis and Alyx's save from being Ground Zero Girl at the detonation of the Combine Teleporter were both accomplished outside of normal timeflow through the efforts of friendly Vortigaunts.