The most universally agreed-upon Game Breakers are Maggie (a revolver with a shotgun spread like the Mashers from the first game, most desired with the "Two-Fer" prefix that makes it shoot twice as many shots at the cost of 2 ammo, or the Dastardly prefix that increases damage, or, if you're playing as Zer0, the Trick Shot prefix, which lets bullets ricochet onto targets and is utterly devastating with Bore), The Bee (an Amp shield that does not drain the shield when you shoot Amp shots), and The Sham (an Absorb shield with at least an 80% chance to absorb bullets, adding them to your backpack and doing no damage to you).
With patch 1.2.0, The Bee got a heavy nerf. No longer does it have the insane amp damage, the recharge delay is longer, and the recharge rate is lower. In addition for all amp shields, on multi-projectile weapons such as shotguns or the aforementioned Maggie, the amp damage divided by the projectile count then added to each projectile. That being said, SMGs like Slagga or Lascaux still have the Bee bonus for every single projectile. This did completely remove the "so hilariously overpowered it's bad" Conference Call shotgun + the Bee combo. (Conference Call generates additional projectiles on hit with an enemy which ricochet back onto where you hit with it. The first raid boss died in seconds to this combo)
The Sand Hawk SMG from Pirate's Booty is now the weapon that gets paired with the Bee. It fires 8 projectiles (in the shape of a bird that actually flaps its wings as it flies through the air) that each get the full amp bonus, and it's a Dahl weapon so it burst fires.
More specifically, The Bee (and all amp shields) have their damage divided by the number of projectiles listed on the item card. This means that unique weapons that have interesting ammo-splitting properties not listed on the card will retain the full amp damage for all projectiles. Sand Hawk, Unkempt Harold, and one variant of The Fibber can get enormous damage boosts from splitting projectiles.
If you climb into a vehicle with the Bee equipped, turret bullets get amp damage. Since you don't take shield damage, the amp damage persists as long as you are in the vehicle. Note that amp damage doesn't apply to other projectiles such as rockets or sawblades, so you get the greatest advantage solo in an MG Runner (or if the passenger also has a Bee shield equipped). The Sand Skiff gains no advantage from the Bee as it does not fire bullets.
Maggie? Not anymore. It's been long established that the highest-damaging pistol in the game is by far the the Unkempt Harold, a legendary Torgue pistol that shoots gyrojets that split into seven. Throw in the "Laser_Double" accessory, and you get the Double Penetrating Unkempt Harold, which fires, well, double the amount of bullets, and deals considerably more damage.
The Unkempt Harold remains one of the best pistols for Gaige, due to the fact that it is one of a few weapons that always fires its bullets in a set pattern, meaning that even with 600 stacks of anarchy, Gaige can get close to an enemy and fire the Unkempt Harold, and be almost guaranteed a hit.
A combo that can obliterate anything other than raid bosses with 2 seconds of firing (that includes lvl 52 super badasses) is Infinity (high fire rate pistol with infinite ammo and no need to reload), the aforementioned Bee shield, and the Sherif's Badge (a unique relic which increases pistol damage by ~20% and firing speed by ~55%). Even better if you have a class mod that increases firing speed and/or pistol/gun damage, alongside skills with damage boosting effects. Zer0's 0ne Sh0t 0ne Kill skill stands out, since it gives +60% damage to every first bullet in a magazine, which applies to every single shot of Infinity. With the right set-up this can lead to doing over 100k damage per shot.
And another weapon that becomes a monster with such a set-up is a specific variant of the Fibber, namely the version whose bullets split into 9 on ricochet on the first non-enemy they hit. Each projectile gets the Bee damage added, despite the "fix" which prevents additional projectiles to get it.
Anarchy + Close Enough = massive amounts of damage. What makes this truly ridiculous is that while Anarchy and Close Enough are on seemingly opposed skill trees, they're also both Tier 1 skills; you can have Anarchy with a maxed-out Close Enough long before level 20. Your accuracy still sucks though, but even then one could easily rampage through hordes of enemies if done right. Gaige even lampshades it when you get enough Anarchy stacks.
If you want utter havoc, Anarchy/Close Enough Gaige with the Maggie. The usual weakness of shotguns and shotgun-alikes - the trouble in hitting with multiple elements at long distances - stops applying, because as long as the gun is being pointed somewhere with a straight line to a target, Close Enough 5 will cause half of the fragments in each burst to hit, even around corners. And assuming a standard Maggie or one with a relatively mild prefix like Gunstock, you can put out seven shots in a couple of seconds, leading to 42 supercharged fragments of lead and hell bouncing around the place. Worse? This can also be done below level 20 - the Maggie's minimum level is 17.
And another one for Gaige Anarchy/Close Enough builds: The Fibber pistol with a particular barrel. All shots fired by this pistol will ricochet. However, Gaige's Close Enough skill can trigger without applying the damage penalty due to the unique change in ammo types after ricocheting (somehow, the ammo transforms from pistol bullets to shotgun pellets). Combine this with the Bee shield and Gaige can be a powerhouse.
Torgue weapons count for both grenade and gun damage boosts. Axton has many skills that boost both. Axton + Torgue weapons = so many explosions.
His gun and grenade boosts also affect the damage done by Tediore reloads. This allows him to take out Hyperius the Invincible at OP 8 with the Avenger and a Bee in three seconds. You heard me. Three seconds.
Gaige's Blood-Soaked Shields talent gives her a substantial shield refill (maxing out at 100%) in return for a hit to health (maxing out at -5%) every time she kills an enemy. It's intended to turn her into a type of Glass Cannon, and it works pretty well for that purpose. However, combine it with Captain Blade's Otto Idol, which restores a percentage of health every time you kill an enemy (at the cost of a shorter Fight For Your Life time), and the health hit is completely obliterated.
Evolution, an elemental resistance shield with a very, very high resistance and health regeneration. Most shields in this category resist anywhere from 10-30% of elemental damage; Evolution usually has around 75% resistance. Its only downside is a lower-than-average capacity, low enough that a level 50 Evolution will not be practical for carrying into Ultimate Vault Hunter mode.
The Vladof Sniper Rifle Droog comes with its manufacturer's characteristic rotating double-barrel giving it ridiculous firing rate as well as paired with a high count magazine, effectively making them assault rifles with ridiculously high base damage, as well as highly accurate when scoped. This is fair enough for most classes, since the limits on the amount of sniper rifle ammunition are very strict compared to most other types of weapons, meaning that even with full ammo upgrades a player will usually only be able to use a couple of magazines before their ammo is depleted. The problem arises when these sniper rifles end up in the hands of Salvador, who rapidly generates ammo during his ability and can possibly pick up Ammo Regen as a perk for his class mods; and because no-scoping is still fairly effective at close to medium range, he can use it in place of an assault rifle or SMG. By itself, this ensures that he will effortlessly cut down almost anything in his path, since his ammo regen is almost perfectly on par with what he's burning through; combined with almost any skill in the Rampage tree, especially "Inconceivable" or "5 Shots or 6", which drastically decrease the odds that he'll even need to reload for the duration of his ability, meaning he can fire without pause for as long as it lasts, turning him into a "Instant Death" Radius on legs. And as if that isn't enough, he'll still have a second gun on hand during the rampage, meaning that he could possibly use TWO of these at once if he's lucky enough to find them. Worse still is the "Lyuda/White Death" Legendary Variant of the Droog, which not only take the damage and magazine way past 11, (Up to over 70000 damage on UVHM even without the bonus from all Vladof parts, and 42 rounds with the proper class mod, skills, and Badass ranks) but makes the bullets split into three after a certain distance.
The Antagonist is basically an Infinity Plus One Shield. Of course, the only way to get one is to farm raid bosses on Ultimate Vault Hunter Mode until you have enough Seraph Crystals to buy one, meaning you likely won't have anything to use it on except for farming the raid bosses some more.
There's an exploit that lets you kill the storyline final boss, The Warrior, with ease. You start on a bluff with The Warrior in a crater below, which you need to leap down to start the fight. If you die, you're sent back to the bluff near an ammo vending machine, and The Warrior continues his attack pattern. To prevent you being able to shoot The Warrior from the bluff after the battle starts, a large shield pops up that blocks all shots. However, not only is the shield not tall enough to keep some shots from hitting the very top of The Warrior, but the cliffs surrounding the shield have cracks in them, letting you easily take potshots at The Warrior when he leaps to either side. Thus, you can just stay on the bluff and shoot The Warrior until he dies, with no chance of any of its attacks hitting you. You don't even have to worry about running out of ammo, since you start next to an ammo vending machine!
Or just use Gaige with Close Enough. Yep, you can kill final boss with lv.6 character.
Alternatively, you can also hop up on to the spiky formations along the left side of the path, allowing you to get a good shot on the Warrior regardless of its position.
There is also an exploit where it will make the Fibber (A Hyperion pistol with sarcastic stats) deal the amount of damage that is says on the card. Meaning that a level 20 fibber could potentially deal the same damage as an ordinary level 45 Hyperion pistol.
The Mechromancer's special ability Deathtrap is also insanely powerful thanks to the Best Friends Forever skill tree. Among the powers it grants are: 20% Cooler, cooldown reduction, allowing a player to summon Deathtrap more often. Upshot Robot, an ability that extends the length of time that Deathtrap can be in effect, based on how many enemies you and it can kill, and this ability boosts Deathtrap's strength with each and every kill. Explosive Clap, a special ability that can wipe out entire groups of enemies instantly. Buck Up, The ability to recharge a character's shields in seconds. Oh, and Deathtrap can levitate and move through walls, and can shoot lightning bolts at flying enemies. The final skill in Best Friends Forever, Sharing Is Caring, will give Deathtrap a copy of your shield, which, depending on the shield you have, can be a devastating power to have. Your Robot Buddy can be death incarnate for enemy hordes.
With the Ultimate Vault Hunter patch and the level cap increase, it gets crazier: each still tree has a few perks that boost Deathtrap's skills in some way. At high enough levels, Deathtrap gains increases to base melee damage, movement speed, laser beams, chained melee attacks, the list goes on and on.
A combination of Upshot Robot and Sharing Is Caring can lead to infinite money if you happen to be patient enough. The Final Boss arena happens to have incredibly weak Rakks flying overhead. The thing is, they continue spawning even after the Final Boss is dead and never stop. Setting up Deathtrap with a health-regenerating shield and Upshot Robot, he'll continuously one-shot kill them and have his duration reset itself constantly. All you have to do is wait on a slightly-elevated pillar to keep him from clipping through the ground, and occasionally run around to pick up all the dropped money and weapons.
The same trick also generates XP. It's slow and boring, but it can be left unattended indefinitely.
Infinite ammunition weaponry. Extremely rare and, if discovered early on, you'll swiftly outgrow their base damage, but once you find them, there's not much that's going to stop you for the next twenty or so levels.
Krieg with grenades and explosive weapons. Strip The Flesh boosts the damage that all explosive attacks can do. Blood Bath gives a bonus to weapon damage based on the number of bloodlust stacks you have if you kill an enemy with a grenade... or an explosion. The increase is .5% per bloodlust stack, meaning that after a kill, you can get a boost of up to 50% weapon damage. Salt The Wound increases shotgun damage up to 20% based on damage taken when shields are down. Add all of that together with a class mod that boosts explosion damage and/or the skills in question, and with a Torgue shotgun, Krieg becomes a murder machine, dealing double the damage that his weapon would normally deal. Even without Salt The Wound, a Torgue Pistol or Assault Rifle is a weapon of mass carnage in his hands.
Alternately, Release The Beast, the final skill on the Mania tree: Trigger Buzz Axe Rampage when at 33% health or lower, and Krieg instantly gets full health, 50% damage reduction, a huge increase in melee damage, and as soon as the rampage ends, Krieg can instantly trigger another rampage, normal, or superpowered if you were knocked down to low health while you were taking out enemies.. So if you were reduced to 33% again, you can trigger another transformation. You can quite literally chain this over and over until every enemy in a wave is dead. 33%, by the way, is what you'll normally be at when you come out of Fight For Your Life mode.
Krieg's Bloodsplosion skill, combined with a Roid shield and a Rapier, is ridiculously powerful as well. Bloodsplosion blows up enemies after you kill them, adds overkill damage on top of that (which is why you want to maximize your single-hit damage in melee), and does 5% more damage per bloodlust stack (maximum 100, for a 500% boost in damage). The increased explosive damage and grenade damage from several of Krieg's skills, as well as those from relics, similarly apply to the explosion's damage. What makes this game breaking? Bloodsplosions chain, and the overkill damage stacks. One high damage melee attack on a weak enemy can clear a room. Add slag into the mix, and you're doubling not only the damage from the melee attack, but the damage from the Bloodsplosion. Used correctly, with properly-grouped enemies, Bloodsplosion can take out several of the game's raid bosses in 2 attacks (one slag, one melee), as the damage keeps increasing as enemies explode, eventually reaching the display cap of 999999k.
With a bit of patience, Krieg can easily pull off a stupidly broken combo early into True Vault Hunter Mode with Bloodsplosion (easily obtainable during a Normal Mode playthrough) and a Fastball Grenade (a Legendary Drop from farming Boll during the In Memoriam sidequest). Fastball Grenades lack explosive radiuses, but make up for it with the best raw damage per hit of any grenade in the game. Hitting a weakened enemy with a Fastball transfers almost ALL of that ludicrous damage into the Bloodsplosion... which, to put it bluntly, means everything within range is going to die. Followed by everything within range of THEM. Followed by... well, you get it.
In Mister Torgue's Campaign of Carnage, there is a set of racing side quests, the last of which is lvl 49, and is almost unbeatable... almost. In another sidequest, you can get a relic that improves your vehicle's boost, so you can boost longer and more often. It is possible to win the side quest with this relic equipped, and the exp reward is quite substantial, given that the quest is so high level. The quest is infinitely repeatable, and takes 2 minutes, win or lose, with no enemies to fight save for the much lower level standard fodder that dwell in the Badass Crater Of Badassitude. If you master the course, you can level up extremely quickly.
In Tiny Tina's Assault on Dragon Keep, there is a gun called the Grog Nozzle that does about a fifth of the damage of comparable weapons, but you will regenerate health equal to 65% of any damage you deal (from any source) while wielding it. That on its own is pretty good, especially if you've got a good action skill or grenade. However, on top of that, there's a chance when you pull it out that you'll get "drunk," which drops your accuracy and causes you to fire six bullets instead of one, for the cost of one bullet. Even better, if you switch weapons, the effect remains for a little while, so you can multiply the damage of any weapon by six. Combine with Gaige's Anarchy and maybe a Bee shield, and everything dies very quickly. The only downside is that it's a mission weapon, so if you turn in the sidequest, you lose the gun. However, since the actual reward from that chain of quests is lackluster, most players just never turn it in.
If you are using Salvador, the projectile split happens to whatever gun you're holding in your right hand while gunzerking. And the healing effect applies to the second gun as well. YOU CAN'T DIE. PERIOD.
Grog Nozzles dropped legitimately from the Gold Golem for one day during the $100,000 Loot Hunt, meaning not only can you finally turn the quest in, but you can actually get one that has the prefix you want and have it stay that way (the one you get during the mission is randomized when you load up the game).
The Norfleet and Sham combo, often dubbed "Shamfleeting". The Norfleet is a legendary rocket launcher that fires three powerful balls of energy with a large Area of Effect. The Sham is a shield that has a chance of absorbing incoming gunshots or explosions into your ammo pool all the way up to 94%. The AoE from the Norfleet's energy balls are large enough that, at the proper range (close but not too close) and with the Sham equipped, it is possible to reabsorb your own rockets as you fire them, effectively giving you infinite ammo for perhaps the most powerful rocket launcher in the game.
Many people also combine the Sham with a low-leveled Logan's Gun, basically trading pistol ammo for rocket ammo and not instantly downing themselves on the rare occasions the Sham doesn't absorb the ammo.
Another combo that restores rocket ammo is a Thunderball Fists pistol (double your chances with a Binary) and The Transformer shield. Shoot the ground at your feet to recharge. Not all surfaces work, but solid ground is a good bet. Self damage depends on several variables, but generally it's fairly safe even with a leveled weapon — meaning you don't have to lose an inventory slot by carrying a useless weapon just for the purpose.
The Badaboom (especially a low-level one) is also a popular rocket ammo restore weapon when used with a Sham. The Badaboom is itself a rocket launcher that fires six rockets at the cost of 1 ammo. Compared to non-rocket weapons like Logan's Gun, the Badaboom requires you to have at least 1 rocket ammo remaining to work, but essentially conjures rocket ammo out of thin air like the Norfleet rather than converting your other ammo types. It is actually more efficient than the Norfleet in terms of ammo regeneration (which only fires three energy balls compared to Badaboom's six rockets), but is considerably less potent in combat and thus will likely take up a valuable inventory slot if you want to use it outside Sanctuary.
The Avenger, a Pearlescent SMG, regenerates SMG ammo as long as it's equipped. If you dual-wield a pair of these while wearing a Hoarder mod you'll find it virtually impossible to run out of ammo before you run out of targets, even without using other ammo-conserving skills. The Avenger isn't very powerful but has decent fire rate and accuracy stats and, as a Tediore weapon, a very fast reload. Just beware their tendency to bounce off nearby architecture and return to you before exploding.
Gunzerking + Rubi + Infinity = god mode. Specifically: all of Moxxi's signature weapons heal their wielder by a percentage of damage done to an enemy while they're the active weapon; Rubi has this effect to the greatest degree short of the Grog Nozzle. The Infinity is a rapid-fire pistol which doesn't consume bullets and never needs reloading. Combine the two, and as long as Salvador has something to shoot at, he can get near-constant health regeneration that can keep up with any enemy short of a raid boss. If he's got a slag variant of Rubi, it goes Up to Eleven because the slag effect will increase the amount of damage done by the Infinity, which will increase the amount of health Salvador leeches from his target, turning his shields into an afterthought.
Oh and another really cheap combo of Grog nozzle's is the Lady Fist, a subpar Hyperion pistol with the redeeming grace of utterly insane critical hit damage. The Grog nozzle also boosts crit damage by itself, leading to a Crit while dual wielding these two to do 2400% damage. While you have to headshot, it's a Hyperion, meaning rapid-fire headshots are stupidly easy, watch Zer0 hang his head in shame for not being nearly as good a headshotter.
Many will opt for a Double Penetrating Unkempt Harold over the Infinity. If Rubi + Infinity makes Salvador a god, then Rubi + DPUH makes him every god in every religion put together.
And if they get the above mentioned Droog? It'll make him the god of gods.
Add the Lyuda/White death and you are truly breaking the game so much that it is rare that the FBI didn't get you in prison.
Just to break down how utterly effective this is, Lyuda fires what's basically 3 rounds for the cost of one, already very powerful, now add grog nozzle, which is always slag, doubling Lyuda's damage, so your more or less dual wielding lyudas at the ammo cost of one. further add in that since you're salvador, you'll be fairly accurate firing full auto, thanks to "Steady as she goes" letting you more or less fire full auto at medium-long range. The only time you're not that accurate is when Grog Nozzle makes you drunk. that's when the fun begins since each shot will instead be 6 less accurate shots, all of which break into 3 so you're basically shooting the equivalent of 18 droogs at once while healing for over 60% of that damage, now remember that you're Salvador and most likely taking full advantage of this sheer convenience by using Brawn/Rampage, which means you'll be gunzerking almost all the time and basically regenerate ammo faster than the Lyuda shoots it out. if you're doing this right, it is literally impossible for you to lose.
What's even better than all of those combined? Grog Nozzle and Topneaa. The Topneaa is a rapid fire E-Tech Vladof rocket launcher with low ammo consumption and massive power and an AOE roughly the size of a normal building. With enough points in "5 Shots or 6" via the use of Hoarder Class mods, you can literally gain ammo from shooting it, You can literally be using a Rapid Fire Rocket Laauncher and Gain ammo from shooting it. It only works when you get kills yes, but when won't you get kills with that thing?.
How about the Hammer Buster rifle? Sure, it's your standard Jakobs rifle and a rather plain legendary...until you get one with the "Horse" prefix, which adds a foregrip and whacks up stability by 50%. As well as that, the rifle has the Dahl barrel, which also bumps up stability and accuracy. Basically, you keep high damage while negating the infamous Jakobs recoil down to almost zero. And there's a hidden 150% critical damage bonus, so now that the recoil has been negated, you may now use the AR as a sniper rifle. Plus, when you're Gunzerking, the new massive stability pretty much flat-out kills any chances of missing, and, with the high-damage and fast fire rate standard to all Jakobs weapons, you can obliberate tough enemies in seconds, and unlike the DPUH, you will be able to hit flying enemies easily. Combine it with the Rubi or Grog Nozzle, and you'll be dealing out damage fast enough to heal instantly. Finally, if this wasn't overpowered enough already, get a Hoarder class mod and watch as any increased ammo consumption from firing as fast as you can click or blasting Rubi goes out of the window.
Fastball grenade, which lacks an explosion radius, but makes up for it with crazy damage output, can be game-breaking in hands of a Syren. Phaselock an enemy (or a group of enemies if you learned Converge), pulling them out of cover and making them immobile, throw a Fastball, boom, gone. Minibosses don't stand a chance.
Krieg using Flame of the Firehawk and a Singularity grenade is just flat out cheap, especially if you equip a Grog Nozzle, whose damage won't matter since you'll never shoot it, it's just there to heal. The Flame of the Firehawk lets you constantly generate burning explosions when your shield is down; Krieg's gameplay involves not wanting shields anyway, so you always drop a singularity grenade when you enter Fight For Your Life thanks to Pull the Pin, which drags people near you so that your constant burning will kill them, and if it doesn't, Krieg has light the fuse, meaning anyone nearby will be pulled in, exploded once by the grenade, constantly burning from the shield, then exploded again by Krieg. If anyone in that mess dies, Krieg gets Second Wind. This puts him just low enough to use Release the Beast, fully healing him and well, look at Release the Beast above, and as soon as his shields inevitably go back down, the burning continues, and Krieg has an entire tree based on fire damage, you'll hit people enough with fire that you will be permanently on fire, and thus take even less damage, you heal even more from fire damage, which you'll be emitting all over the place, add in what Krieg normally does with the stuff mentioned above. Yeah.
It should be noted, however, that all this requires a healthy heap of skill points in TWO of Krieg's skill trees - more than can be racked up in a single playthrough. Atop of that, 'Pull The Pin' only drops a grenade AFTER Krieg died, so no Second Wind here...and 'Light the Fuse' overrides 'Pull the Pin' completely.
The Lady Fist with its 400% (800% after a patch) critical damage turns most encounters into a cakewalk. It can be effectively used without zooming on the sight as continuous fire will put a very precise stream of high damaging bullets on the enemies' critical spots. A corrosive Lady Fist will dismember loaders quickly, and incendiary variants can be used to lethal efficiency on flesh targets. The Lady Fist is one of the few weapons that doesn't lose the reverse recoil bonus during reload times, effectively retaining almost full accuracy after magazine reloads in combat situations.
The gunzerking skill Money Shot. it's a skill that gives a huge damage boost to the last bullet in the magazine. By exploiting a glitch, you can make it so that you can chain Money Shots repeatedly and bring down bosses like Terramorphous before they even have a chance to fight back.
The Chaotic Evil Monk class mod from Tiny Tina's Assault on Dragon Keep adds an extra six points to Money Shot. Need I say more?
Believe it or not, the highest-DPS weapon in the game is actually the Pimpernel, a Maliwan sniper rifle that you get from the mission "Don't Copy That Floppy" in Captain Scarlett and her Pirate's Booty. Unless you're playing as an Anarchy-centric Gaige, you simply aim at the "sweet spot" of your target (in most cases it's the crotch), and you can annihilate enemies instantly, even in UVHM where sniping requires different tactics due to the drastic enemy health increase and is thus often abandoned by many players.
Think the Pimpernel wasn't strong enough yet? Play Salvador, put the Pimpernel in the 2 or 4 slots, and put a rocket launcher, preferably Torgue, in the 1 or 3 slots, the best ones being the Ahab for its Damage and the Creamer for its Moxxi effect, although good runner-ups include the Norfleet and Nukem as well as any old Torgue Rocket Launcher. Make sure you have Money Shot active and then empty all your rocket ammo into the sky, Gunzerk with the empty launcher in your main hand and the Pimpernel in the other. Kill raid bosses in a single magazine and Go over the game's ability to display damage.
Various weapon effects aren't actually traits of the weapon, but "buffs" they cast onto the user that affect their weapon, usually the same weapon that buffed them in the first place. Salvador can dual wield, gaining the properties of one weapon's special ability and putting it onto another. Given that quite a few of them rely on their buff to be worth anything that buff becomes incredibly effective when put onto an already powerful weapon. Good examples are the Grog Nozzle, mentioned above; the Orc, with its ability to split projectiles and majorly boost fire rate and reload speed; the Ogre with its similar but less powerful buff makes up for it by already being a BFG in its own right; the Evil Smasher, which can go from one of the worst guns in the game to a above-average one through a flat out "Buff everything until the Evil Smasher reloads again" buff that lasts forever if Salvador simply holds the evil smasher in his offhand and doesn't reload it; the Tresspasser, a below-average sniper rifle that can bypass shields, which is given to the other gun as well, being especially nasty if it's a fire or corrosive weapon on fleshy and armored targets respectively.
Axton's skill Grit gives him a chance to straight up avoid death. It has a percent chance to activate when Axton takes mortal damage, but what the game does not tell yo is that it STAYS active for a few seconds, making Axton briefly immortal. Maximizing the skill with a Legendary Pointman class mod makes death a coin flip. This has led to many instances of players simply standing around and shrugging off literally every enemy attack that hits them.
In co-op it's possible for an Axton player (as long as they aren't the host) with at least one skill point in Expertise to perform a glitch that increases his regular movement speed. This is stackable so that he can move even faster than a speeding car. This speed sticks with him even when moving between different areas, but is reset when the game is exited.
It's not possible until at least Level 51 (due to requiring skills from three separate trees, one of them being the capstone ability for that tree), but Krieg can unlock a trio of skills that turn him into a nigh-unkillable juggernaut. With maxed out Taste of Blood, Numbed Nerves, and Release the Beast, Krieg can maintain a natural 87.5% damage reduction— or in plain English, he'll only take one-eighth of ALL damage, WITHOUT factoring in class mods, relics, shields, or weapons. Granted, this requires having maxed out Bloodlust stacks, being at 33% health or lower, and being on fire (though he can set himself on fire), but for the most part this isn't too difficult to manage with a few more skill points. More to the point, Krieg can fully heal himself after every melee kill under Release the Beast, which isn't hard to do seeing as Krieg's melee damage scales to his level AND gets a 100% melee boost under Release the Beast. By the time Krieg reaches the level cap, he can pull this off ON TOP of the aforementioned Bloodsplosion and Strip the Flesh (which will likely be picked up on the way to Release the Beast anyway), turning him into both a nearly indestructible tank and a GOD of melee and explosive overkill.
The Bonus Package is a Legendary MIRV Grenade that has an increased chance of spawning from the second bosses in the game, Boom and Bewm. It's a MIRV Grenade that, on top of producing a wave of grenades upon detonation, produces a SECOND wave of them when the first wave explodes. It's ridiculous at clearing rooms, especially once you've expanded your grenade ammo, but what brings it into Game Breaker territory is how easy it is to farm. As mentioned earlier, it comes from only the SECOND boss in the game— but it also drops from BOTH members of the pair, providing two chances to pick one up per farming attempt. To top it off, it works for both Krieg's Bloodbath skill (which increases the odds of dropping grenade ammo with grenade kills, making it absurdly sustainable) and Salvador's Double Your Fun skill (which spawns a second grenade per use at no cost, meaning there will be FOUR MIRV blasts and increasing the odds that there will be no survivors)
From Tiny Tina's DLC, you can obtain from the Wizard enemies "spells", which are simply grenades with effects. Not too promising, right? Well, every one of them has the effect of regenerating grenade ammo naturally every few seconds. Ok, not bad. Then there's Magic Missile. The blue rarity Missile sends out two homing orbs, and the purple sends out four. They home in on enemies, and explode on contact. Getting better. The best part? They are Slag elemental. Yep. That means in UVHM, you can have a self-regenerating supply of tracking, instant-exploding Slag grenades for any class and build to make life easier for you and your friends.