Game Breaker/Tabletop Games/Tabletop RPG

"Most of it falls into three categories: broken, very broken, and holy God-Emperor what is that abomination."

- RPG.net combat optimiser Jon Chung, on the Scroll of the Monk for Exalted

Game Breakers in Tabletop RPGs. While any option or combination of traits not explicitly denied to the players will get tried, only a fraction of these builds see actual use due to GM oversight.

Dungeons & Dragons

 * In Dungeons & Dragons 3.5, using the Serpent Kingdoms Sourcebook it's possible to construct a perfectly legal character (a kobold dubbed "Pun-pun" by its creator) who possesses every ability in the game (including godhood) at infinite strength and is immune to all negative effects... at level 1. This combination does require assuming a certain intelligent NPC involved in the process (and by extension, the DM) to follow a very specific script without any deviation, as well as asking (and trusting) an Efreet to grant you three wishes for no compensation (or allowing it to enslave or murder you on the spot). There are slightly more delayed/demanding versions that don't involve this Batman Gambit or cheesing off of genies, however, only requiring you to get up to level 5 instead of requiring the rest of the universe to conspire in your character's favor.
 * Many of these to be found in Dungeons & Dragons 3.5, a few of which do not even require sourcebooks outside of core (Pun-Pun is only the most famous as he basically amasses all of the others' powers). A full list of these may be found here along with explanations. Yes, the official D&D forums have an entire board dedicated to the pursuit of the most hilarious/demented Game Breakers ever (though the logic behind many of them is equivalent to "But the rules don't SAY dead people can't keep fighting and taking actions!").
 * And it's not all about character design or game mechanics either. For instance, a 10 foot ladder is cheaper than two 10 foot poles, allowing for an infinite money loop and infinite firewood. (Think about it.)
 * Another Tabletop Games example: The haste spell in Dungeons & Dragons version 3.0. Originally redesigned the way it was to "show off" the new action rules, designers learned the hard way that there was such a thing as an action "economy" in their resulting game... and whoops, they broke it. Nerfing this spell was arguably one of the primary reasons for the creation of 3.5.
 * To make this one step worse, the "speed" armor enchantment permanently duplicated the haste spell and was cheap which wouldn't have been so bad except then the Arms and Equipment Guide established that armor enchantments could be added to bracers of armor which could be worn by characters who don't normally get to wear armor. Every mage in his right mind bought a pair as soon as he could afford them, as an item that grants +1 armor bonus, +4 dodge bonus, AND lets you cast twice as many spells per round without having to ever take the action to cast Haste is a steal at 16,000 gp.
 * D&D 3.0's Harm, full stop. A touch attack that leaves a target with 1d4 hp. That's right, the more hit points a target has, the more damage it's going to take.
 * It did the same in prior editions: 3rd edition simply put in a Hit Points system that broke Harm completely compared to all the other damage spells. While the Hit Points of your average non-Mook increased about fourfold, all the damage spells did the same damage. Result: Fireballs and lightning bolts lost 3/4ths of their effectiveness, Harm lost none.
 * Yet another D&D 3.5 example: the Hulking Hurler Prestige Class. The damage of a thrown object is proportional to its mass and limited only by your carrying capacity. If you qualify for the class at all, it's a one-hit-kill. Optimized HH builds have been known to do TRILLIONS of damage.
 * The supposed 'balancing factor' for the Hulking Hurler was that it required the character taking the prestige class to be Large size or larger, which put it out of reach for most PCs without taking a truckload of monster hit dice or level adjustment. It probably wasn't meant to be used by player characters at all, but players found ways around the restriction (such as enlarge person with permanency).
 * Or the goliath race, which counts as Large for some things and can get a barbarian racial substitution level which increases their size to Large while raging. Which means for the low, low cost of a +1 level adjustment you may now play your Hulking Hurler, Incredible Hulk-style (as long as you happen to be actively raging the exact moment you level up, every time you level up, as that is a prerequisite to taking any levels in the class in the first place).
 * Another D&D version involves what is typically dubbed the locate city bomb. There is a spell called "locate city" (a harmless divination spell that does Exactly What It Says on the Tin), which has a radius effect of 10 miles per caster level. One then uses an obscure series of feats to first give it the Cold subtype, then deal 2 Cold damage to everything in the area of effect, then change it to an Electric type spell. You can then use another feat that gives an Electric spell a Reflex save, allowing you to apply the Explosive Spell metamagic to "locate city", forcing a second Reflex save to avoid being blasted to the edge of the area of effect. Failing this save will deal 1d6 damage for each 10ft travelled, allowing someone to instantly wipe out a whole city of commoners with no collateral damage (except for the blood splatters).
 * One noted problem with this spell is that the same very unusual area of effect that gives it such a noteworthy large area also makes it definitionally two-dimensional (the spell explicitly affects a circle - not a three-dimensional area like a sphere or one of the normal areas of effect). The damage is based on the distance those within the spell must be propelled to be ejected from the area - which depending on the elevation of the spell and their height may be just a few inches or feet straight up or down, if they're affected at all.
 * Modify the spell to deal ice damage then add in Fell Drain. A Fell Drain spell automatically gives everybody in the area 1 negative level... which will kill any level 1 commoner with no save, and they'll turn into a wight. When the wights are all up, they can go kill everybody who wasn't killed by it. The fun part is that the PCs all will survive this combo easily, while the original combo, if it worked, would kill all of them as well.
 * A simple 3.5 spell which is not high level, does not appear exclusively in an obscure sourcebook (it's in the Player's Handbook), and doesn't require a cheesy combination to work is the level 3 Bard spell 'Glibness'. In a game system where +4 or +6 to a roll is considered a considerable bonus, Glibness gives +30 to your bluff checks for its duration (10 minutes per caster level, a minimum duration of over an hour). The penalty to your Bluff skill check for telling a lie that is completely and utterly unbelievable ("I am the Moon.") is only +20 to the DC. With Glibness, you can quite easily convince a king that you and he were actually secretly swapped at birth and that by all rights he's sitting on your throne. This is the kind of simple, elegant spell that can make a GM go "What the ^%$##*@!^?!". Glibness' power was highlighted to great effect in an Order of the Stick strip. Yeah, that describes it nicely.
 * Glibness can be seen as a subset of the entire game breaker that is otherwise known as the Diplomacy skill. Under the rules as written, it requires a result of 50 to turn someone willing to take risks to hurt you (Hostile) into an ally willing to take risks to help you (Helpful). Considering it's legally possible to build characters who get +72 to their Diplomacy rolls by level 6, in theory you need never carry a single weapon nor fight anyone in your life, since you'll only have to open your mouth for roughly 10 seconds to enlist the help of virtually anyone who wants to hurt you.
 * Of course, you have to have a common language (or other way to communicate) and the things trying to hurt you have to be smart enough to understand the concept of "friend" (and preferably not in a fundamentally unhelpful way), so it's not foolproof.
 * Blink, Ethereal Jaunt and similar spells which let the caster pass through walls and ignore attacks have been the bane of many an unseasoned DM. Heck, just about everything on the Story-Breaker Power page is available as a spell.
 * It's hard to find a use for Invisible Spell (viewers cannot tell that your spell has taken effect) that isn't overpowered. Common uses include Invisible Summon Monster, Invisible Fog Cloud (only obscures the vision of creatures who can see invisible things), Invisible Invisibility, and Invisible True Resurrection.
 * By combining feats from multiple sourcebooks, it's possible to reduce the cost of Bestow Power (transfers psionic energy to another creature) until it can transfer at greater than 100% efficiency, allowing a character to recharge their psionic abilities between fights. This wouldn't be as notable if psionic characters didn't have the ability to boost the strength of their powers by expending larger amounts of energy (meaning that a character using this trick can "go nova" in every fight with no consequences).
 * Even sticking to core, Druids have powers (casting, wildshape and animal companion) that a single one of alone would be a competent character. They have special abilities that are more powerful than entire classes.
 * To put this one into perspective, there is a ranking of the classes based on power and versatility, from tier 1 (can solve almost any problem easily) to tier 6 (no useful abilities). Druids are of course tier 1, and there are no non-spellcasters above tier 3. As an example, the guy who built the system showed a variant where all spellcasting became extremely difficult, knocking most spellcasters from the lofty heights of tier 1 and 2 down to tier 6. Druids however were still at the high end of tier 3. Why? A single class ability of course: Wild Shape, an ability that is in and of itself more powerful than a Fighter's whole class (indeed, a Ranger variant with a nerfed version of Wild Shape as its primary ability is at the low end of tier 3). Actually, twinked out animal companions are stronger than Fighters. There's a reason why CoDzilla (Cleric-or-Druid-zilla) became a DnD meme.
 * And once you get out of core, there's the ludicrously overpowered Planar Shepherd, which happens to be custom made for Druids (and possibly the only Prestige Class strictly better than more Druid levels). Other gamebreaking prestige classes include the Dweomerkeeper, famously used in the "Cheater" (Chosen) of Mystra, which could circumvent almost all all the restrictions on Wish and Miracle, and use both multiple times per day.
 * Finally, in our survey of D&D options which don't rely on an unforeseen combination of feats and/or spells to break the game, consider the spell Shivering Touch from the sourcebook Frostburn (and well you should, since the game's creators clearly did not). When you cast it, you touch your target (usually not hard since D&D's combat system tends to focus around getting through armor to inflict damage rather than simply touching them - though spellcasters or creatures with certain exotic or class-granted defense bonuses may have very high touch AC). That target then suffers between 3-18 points of damage to its Dexterity. Because the aforesaid monsters generally have a low Dexterity, depending on how well you roll this will actually penalize an opponent's AC by up to -5 if you take their Dexterity to 0, and also render them unable to move. The phrase 'sitting duck' then applies to your opponent. As an added bonus, unlike most other seriously powerful spells in 3.5, Shivering Touch does not allow a saving throw against it. The only beasts that stand a chance of avoiding death by clumsiness are those with spell resistance. Not bad for a spell which any cleric or wizard can cast from level 5; in some spheres this spell is called the dragon killer. And that's even before you look into things like applying metamagic to it.
 * The Erudite class in 3.5 is not broken in and of itself. It has the ability to eventually learn every psionic power there is, but this just makes it the psionic equivalent of a Wizard, whereas other psionic classes would be focused spellcasters like Beguilers or Warmages. The "Mind's Eye" series of columns on Wizards of the Coast website, however, provides an alternate class feature called Convert Spell to Power. For the cost of giving up a single bonus feat at 1st level, this feature grants Spellcraft as a class skill and allows the Erudite to use it to study any arcane spell, convert it into a psionic power, pay a small (e.g., 400 XP at 20th level) cost to permanently learn that power, and then use it at will for as long as their Mana Meter holds out. So not only is your Erudite a psionic-type Wizard, he's now also a mutant wizard-type Wizard that can spontaneously cast like a Sorcerer and isn't subject to arcane spell failure.
 * Perhaps even more alarmingly, the spell-to-power Erudite can even ignore costly material components.
 * Want to destroy the world? Pick a melee class. The metabreath feats in the Draconomicon allow a creature with a true breath weapon--which was not available to players at the time without jumping through a lot of hoops--to improve the damage/range/staying power/etc. of a breath weapon at the cost of extending the cooldown between uses, and they could be stacked with themselves. A 5th level green dragon shaman with 17 Constitution and the feats Enlarge Breath, Clinging Breath, and Lingering Breath could, in a single round, theoretically create a cloud of acid the size of the entire planet that lasted for a year or more at the cost of not getting to use his breath weapon for several years. The only problem is that anything that did survive (high-level wizards, earth elementals, etc.) would come looking for revenge slightly sooner than that.
 * Eschew Materials, weak ass feat or subtle game breaker? This feat will let you cast spells without having to worry about inexpensive material components, provided they cost less than 1 GP. Unfortunately most of the times won't come into play and doesn't take care of the expensive components, which most of the times are the ones you care about, such as 500gp valued Diamonds etc. Generally it is used when you don't have free hands to use or as a contingency when you don't have access to your component pouch. This feat has been used with a couple of spells to produce weird effects, like the spell Launch Bolt from Spell Compendium, which launches a crossbow bolt, requiring a ranged attack roll to hit. Since it lists the crossbow bolt as a material component, you can employ Eschew Materials to cast launch bolt using a bolt of your choice size-wise, so you can cast a cantrip and launch gargantuan bolts (crossbow bolts cost 1 sp and +1 sp for each size increase, so gargantuan ones cost 8 sp, which is under the 1 gp of free materials you're able to cast with this feat), to do 4d6 points of damage, USING A CANTRIP, A LEVEL 0 SPELL! Another use is casting fabricate to create really cheap things, without having to have access to the materials beforehand, basically conjuring something out of thin air; you could for example visit the astral plane (or any plane that has the timeless trait - assuming you don't have any aging problems, this is a separate but solvable issue...) and cast fabricate as many times as you can to generate 1 gold piece each time, making you rich in no time when you come back to the material plane.
 * D&D 2nd Edition Skills and Powers had a mage variant called Channeler, which effectively combined mage and sorcerer (you could learn as many spells as you wanted and cast them all however many times you wanted until you ran out of spell points). The only downside? You fatigued yourself when you cast a spell (and yes, you could kill yourself this way). There was an 8th-level spell called Heart of Stone that replaced your heart with a carved stone one. Among other effects, it made you completely immune to fatigue.
 * In the 2nd Edition of Dungeons & Dragons the Psionicist's Dimension Door wasn't limited to vertically standing doors. Open a horizontal door below your target, put the horizontal exit above them. Let them fall for a while (the disorientation effect keeps them from casting or doing anything to save themselves). This either ends with the target being cut in half by a closing door or splatting against the floor. Good fun. Meanwhile the Psi is constantly getting EXP for expending power points. That's thinking with portals.
 * D&D 4th Edition has has a large number of infinite combos IN THE CORE RULES:
 * There is a 15th level Ranger power called "Blade Cascade," which allows multiple hits as long as the previous hit connects. This inspired game-breaking accuracy builds; one such (Kenshiro "Ratata" Orcuslayer) could kill Orcus at level 15 as long as the player did not roll a 1 (which is an automatic failure) on the d20. Wizards of the Coast quickly issued an errata stating that the maximum number of hits on the power was 5 (1 per 1.25 seconds of the combat round).'
 * Sleep is a first level Daily spell that knocks people out, making them vulnerable to continuous Coup De Grace attacks. You can use Salves of Power, (which cost 5000 GP and a Healing Surge) to regain this power. And until recently, getting a -16 continuous penalty to saves was quite easy (now it's basically impossible, although you can still get a fairly high penalty to saving throws for one or two rounds).

World of Darkness

 * In Werewolf: The Apocalypse it was possible, with mere hedging of the rules rather than outright cheating, to make a starting character that rolled in excess of 40 damage dice per hand, and went first in every combat round.
 * Even without any cheating at all, werewolves in the Old World of Darkness could spend Rage to have an extra action in a combat round. Rage replenished every time they got angry--so basically all the time.
 * In Vampire: The Masquerade, one of the most brokenly powerful powers was available at character creation and found at lowly Discipline level 2 of Obfuscate - which let the vampire using it become invisible. No blood or willpower spent, no roll needed. Just plain ol' at will invisibility. Now, there was a counter (Auspex, available to a handful of vampire Clans and even then they had to be at least as good at Auspex than you were at Obfuscate), it didn't fool cameras or other technological systems (not a problem if you're playing Dark Age) and until higher levels in the discipline it dropped when attacking or performing similar attention-getting actions. Still, quasi-perfect invisibility any time you want, in a game that revolves around intrigue, information gathering and general-purpose skulking around ? Sorta kinda neat.
 * Though this breaks the game in terms of the World of Darkness setting and the Storyteller system, you must factor in precisely what they're up against.

Other Games
""It's a cosmic attack, literally. Pulses of cosmic energy that radiate from the attacker (reaching 74 gigaparsecs in a flat second) burn out the neural system of living beings in the affected area, and remember that even the edge of our universe is "merely" about 10 gigaparsecs away from Earth. Also note that an Area Effect attack with Emanation involves no to-hit roll and simply affects anyone in the area. Furthermore, it allows victims only to dive for cover, and actually there's no effective cover since this Cosmic, Irresistible attack ignores DR. In conclusion, the user can attack every living thing in our entire universe, with 1 point of damage, 300 times per second. Have fun. 53 points.""
 * The first edition of Warhammer Fantasy Roleplay contained several somewhat ill-considered spells, the most infamous of all being the innocuous-sounding Glowing Light. Glowing Light is a very basic Petty Magic spell used to turn any handy useless object into a disposable torch. At least, that's what it was supposed to be used for. The spell description actually just said "The object glows brightly for one hour, and then vanishes." And then vanishes. Most novice wizards considered that a one hour time-delay was a fair price to pay for the power to vaporise anything they could lay their hands on.
 * Any tabletop RPG that allows "point-buy" character design is vulnerable to Game Breaker characters. The Variable Power Pool ability in Hero System is particularly infamous.
 * Mutants and Masterminds has been nicknamed "Min-Maxers and Mary Sues" for a reason. 4chan's /tg/ is just full of M&M characters using the gamebreaking for fun. For instance, Ball of Arms Man 360 degrees of punch!
 * In GURPS 4th Edition, someone built an advantage named M.U.N.C.H.K.I.N. that allows you to disintegrate the entire universe for 53 points in a game where a "career adventurer" is expected to start at 200 points.

"Acting Rank 3: "At this rank, the dramatist has gained the ability to physically alter their entire body, so that the dramatist can assume the form of animals. The forms which the actor chooses to become may not exceed the mass of a heavy war horse, and no items (including clothes or weapons) change with the Artisan.""
 * Second Edition Exalted: In a game where defense has primacy, Obsidian Shards of Infinity Form has two scene-length perfect defense charms, one of which allows you to perfectly redirect any attack aimed at you. It lets you make and control a perfect clone of your opponent who is linked to the clonee, and command it to kill itself, knocking the opponent out. A charm to make all of these cost zero essence. These charms are almost impossible to counter, and the chance of someone having IC knowledge of them is low.
 * And then there's the combination of Grandmother Spider Mastery and anything that enhances perception. Grandmother Spider Mastery allows the Exalted to attack everything that he or she can see in a single action. There are charms that allow an Exalted to see everything in several hundred miles, or even everywhere in Creation. Pattern Spider Touch turns a single action attack into a move that either utterly destroys or transforms its target. The natural result of this has been nicknamed Creation-Slaying Oblivion Kick. It does, however, require Essence 7 and a cooperative Sidereal Martial Arts master, at which point killing everything everywhere isn't that far from the norm.
 * The merit Brutal Attack allowed people to use Strength for attack rolls instead of Dexterity. This allowed tyrant lizard totem Lunars to show up as a T-Rex and roll 20+ dice for their attacks without spending a mote.
 * Rifts is a game where everyone is a Game Breaker, and needs to be in order to survive the Nintendo Hard combat, but there's one O.C.C. that surpasses even the most broken Juicer or Crazy Hero. Glitter Boy. A character who gets a several million credit mech suit with around 700+ M.D.C. (Mega-Damage-Capacity). A normal character's armor has about 45-100 M.D.C. (To put this in perspective, 3 MD is enough to tear a car in half, and can kill a human several times over), and has a BFG that can inflict up to 100 M.D.C. or more in a single shot. A Glitter Boy can, with a little luck, survive a nuclear explosion. What's the drawback for all this power? The character levels a little slowly, and they have to get out of their mech for a few minutes a day to prevent atrophy.
 * Magic users can be seriously broken as well; most notable the Ley Line Walker, who starts out with a huge amount of mana/sp, and some of the most powerful magic abilities in the game. And if one is lucky enough to roll good Psionic powers, One-Man Army time. A properly built LLW is capable of withstanding a direct nuke hit by 5th level, and dealing out almost as much damage. And that's before adding insane stuff from magic-heavy expansions like Worldbook: Atlantis.
 * No magic users will ever be without the most broken spell in the game, Carpet of Adhesion; a 3rd or 4th level spell that is ludicriously powerful, able to glue down and glue together literally ''anything', immobilizing most enemies and turning them to sitting ducks. (To make it worse, this spell is available to some of magic user classes at first level.)
 * One of the classic examples is the Godling RCC from "Conversion Book 2: Pantheons of the Megaverse". In that you can combine all the useful special abilities of three core classes, superhuman strength, endurance, and regeneration, a 100,000-year lifespan, and some nifty utility powers such as darkvision, seeing the invisible, etc., all for the price of... it's an allowable starting character class, actually.
 * Then there is the Cosmo Knight from the Phase World sourcebook, who not only is immensely powerful (they're designed to take on starships), but can be combined with just about any other race in the game.
 * Both the Godling and the Cosmo Knight were created by C.J. Carella, who is quite possibly the Biggest Munchkin Ever.
 * CJ Carella should have his own section, the man is/was a human Game Breaker. South America 2 has what is arguably the worst example of broken munchkinism. There is a psychic character class in there called the Gizmoteer. One of his powers is the ability to convert any energy weapon so that it runs on psychic energy instead of energy clips. The cost to recharge said weapon is equal to the weapon's payload. The very same book features a gun known as the Anti-Tank Rifle, a very high powered gun (like, it does more than the Glitter Boy BFG mentioned above) designed for armies to give infantry troops a chance against tanks. The drawback of the weapon is that it drains the entire energy clip in one shot, giving the weapon a payload of one. How munchkins can combine these elements to their advantage is left as an exercise for the student.
 * And let's not get into the stuff you can come up with when you mix sourcebooks and even other Palladium RPGs. One horrific example is the Zentraedi Titan Juicer Murder-Wraith. For the uninitiated, that's a fifty-plus-foot giant zombie with thousands of MDC that can only be harmed by magic or silver weapons. Good luck getting a GM that will allow it to happen, but it's perfectly game-legal. Yet again, C.J Carella was responsible for Titan Juicers and Murder Wraiths.
 * Stun in D20 Star Wars Revised is somewhere between That One Rule and a Game Breaker. If you hit with a stun attack, your enemy must save or be helpless, losing all dexterity, granting a +2 to hit to all attackers, and drops what they are holding for a few turns of combat. If they do save, it happens anyway for one round. Again, this is for every hit, so a party can simply tie up a single, powerful enemy, regardless of size (think rancor) and whittle it down at virtually no risk to themselves. Even if the enemy breaks the loop because all the party members using stun weapons miss (unlikely), they have to take move actions to get their weapons back into their hands, allowing maybe an attack or two before the Cycle of Hurting continues. Do not do this to your players, even as a joke.
 * Another big gamebreaker was one ability of the Elite Trooper Prestige Class, called 'Deadly Strike'. To qualify for the class at the earliest opportunity, one had to be a sixth level Soldier, then gain nine levels in the Prestige Class. Hard to get? Possibly. The benefit for your patience and hard work? The character in question makes a full-round action to perform a single attack, that deals maximum possible damage regardless of a critical hit. This attack has a doubled critical threat range, and gains a plus four to hit. This is coupled with the character's already high plus fifteen to hit from base attack, plus whatever dex bonus they may have, plus any other bonuses, feats, or special abilities to boot! What does this all add up to? On a crit, even with a measly blaster pistol, anyone getting hit dies, and the odds are that the average to-hit bonus is going to be twenty-five before rolling the d20. Couple this with a blaster cannon, the resident energy BFG, and a few good critical hits, and this character has a decent chance of taking out anything less than a frigate in orbit, by himself, from the ground, in roughly two minutes. Any starfighter will be dust in roughly three to five rounds, long before the pilot can even see the tiny speck down on the ground blasting at it. A round being six seconds long, that amounts to eighteen to thirty seconds, per ship.
 * Sen Zar seems to hate the gamemaster with a passion. The "status" power increases a player character's starting money from 1,000 Stars to 1,000,000, in a game with a comically broken artificing system. Proper munchkinisation can result in a player character starting with an armour value of 100, and being armed with a weapon which has a +10 attack bonus, causes an automatic 300 points of damage that will not heal short of 8th Order Magic while healing you for every point it deals, and forces any human you hit with it to make a power save or instantly die. Sen Zar is probably the only game where a starting character can be armed with a weapon able to kill a normal player character 20 or 30 times over.
 * While FATAL is a terrible system, it has one spectacular Game Breaker. Your starting level, instead of being 1 like any sensible game, is the square root of the number of years you've been following your profession. Now, this means that a character who has spent 400 years at their job is maximum level from the get-go. Dwarves have their age rolled on 1d1000, and start work before 200. There's also damage XP, which is awarded per class that gets damage XP - so, if you have a few levels in three classes that gain damage XP, you can level up three times faster than someone playing a pure class. The only counterbalance? The assumed Killer Game Master, and considering your GM is likely drinking heavily in an effort to forget some of the things in the rulebook...
 * In addition, playing a large race and raping enemies in the ear is absurdly easier and more lethal than attacking them normally. Or So I Heard.
 * Just-as-stupid RPG Racial Holy War (yes, seriously) is broken anyway, but even if fearsome amounts of alcohol and inbreeding have convinced you to actually jury-rig the rules into a playable state, you'll still be left with the hideously broken Athlete player class. See, Athletes get an additional 10 hitpoints per level, since the ability of an experienced athlete to ignore a chainsaw to the head or anti-tank weapon is well known.
 * Synnibar, full stop. It is fairly reasonable for a party of five people with a decent starting sum and stats rolls to have every PC have 50,000 Life Points, shotguns loaded with Lubricated Pelleum Steel slugs, and be able to attack three times per segment, twice.
 * A half-pound sling ball of Pelleum can be purchased for nearly 1/200th of the price. After spending the starting funds, the players can have a 100-foot armor-plated pirate ship that could shrug off nuclear bombardment with armor-piercing chainguns and rocket launchers to fire back.
 * The designers of the superhero RPG Wild Talents freely admit that their (fairly generic) powers-creation system can be easily abused if players are so inclined. The 2nd Edition rulebook even comes with a free example describing how to build a power that will allow the character who has it to extinguish the sun...
 * The first edition of the Legend of the Five Rings RPG had quite a few gamebreakers. One of the most infamous was a joint grip maneuver from the "Mizu-do" unarmed combat style. A successful roll could disarm and incapacitate the target. Doesn't sound too bad, except that the target's abilities had almost no effect on the easy-to-perform maneuver. As a result, a starting character with fairly normal stats (Agility 3, Mizu-do 3) would have about a 50% chance of disarming some of the greatest swordsmen in the Emerald Empire.
 * You also get some of the crazies stuff with the Kakita Artisans, who were both underrated and overpowered./tg/ archiveSFW writeup.


 * 4th Edition has the Asako Henshin, who are simultaneously broken in both directions. At first rank, they get an ability that lets them raise or lower anybody's traits of a certain ring, and it lasts for a very long time even early on. So with a simple action, an Asako Henshin can render trained courtiers into gibbering idiots, out-wrestle a Crab, or out-stealth a ninja. However, the rest of the class is broken in the "unplayable" way, with rank 2-5 abilities being mutually exclusive, being conditional at best, and the class lacks the staple 'can make attacks as a simple action instead of a complex action' feature at higher levels, instead getting a watered-down version at rank 5.
 * In Eon, you can create an extremely lethal fire spell that makes any one target within 30 meters burst into flame and keep burning for 1 minute, dealing constant damage to everything within 1 meter radius (which means basically the victims entire body). It's a 3rd level spell, but it deals more damage than your standard 5th level spell (and in this game, that's a pretty big leap in difficulty to pull of). So what does it take to craft this spell? A decent score in fire/heat/chaos magic, an average score in the skill Transform Magic, and two different magical effects. And if you up the level of the spell by a tidbit and add a certain third effect, the fireball doesn't go out until the caster says so.
 * On the other hand, it does have one weakness. Casting the spell requires five rolls on three different skills, and failing any of those rolls means the spell goes of in its unfinished state and the caster has to start over. Of course, this means that if the caster fails on any of the last two roll, the fireball will manifest directly in the palm of the caster. And when a fire with a 1 meter radius manifests with its center right in your hand, yeah you can guess the consequences.
 * The pounce ability in Pathfinder that allows to make a full attack at the end of a charge is quite controversial due to how any melee character can become ridiculously powerful with it. The barbarian can get it as part of a rage power at level 10 and nearly every player agrees that it's by far the strongest power the class can offer. The most egregious case is the summoner and her eidolon. In a nutshell, an eidolon functions similarly to an animal companion but is superior in every aspect, can develop a ludicrous amount of appendages and natural attacks (up to 3 at level 1, 7 at level 20) and can get pounce at level 1! Combine this with other evolutions that improve natural attacks in various ways, the eidolon's good base attack bonus progression and all the boosting spells the summoner has access to and you get an absolute monster that instantly tears an enemy to shreds at every round of combat and can only be stopped by an absurd amount of AC or some huge DR. No wonder the summoner was heavily nerfed in the Unchained optional ruleset that is mandatory for official play.
 * D20 Modern in the Urban Arcana setting allows players to generate characters newly arrived shadowkind. They get an increase in wealth at the cost having no wealth after character creation and not existing. Requiring the wealth be spent on "personal gear typical of a medieval fantasy character" is not a penalty but a bonus: The reason players can't just buy whatever magic items they want is they're rare on Earth. Combine the fact you won't have money leftover anyways and there really isn't a lot of appropriate gear stated up anyways, dumping all your wealth into buying some expensive magic weapons and armor isn't just broken, it's the only rational option. The weird and fiddly wealth system and not being able to have above +0 wealth anyways also mean that since you can just buy anything at or equal to value 20 without penalty so you might as well binge on mastercraft/magic items under that cost to round out your kit.