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 most powerful shields are generally those that have a special effect combined with a high chance to use that effect. Most commonly seen topping the list are The Bee — an Amp shield that does not drain the shield when you shoot Amp shots and thus allowing you to shoot many more 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. Other absurd combos and strategies with The Bee include the following:
The Sand Hawk SMG from Pirate's Booty is the weapon to pair 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 with its Dahl aim down sight, its burst fire shoots of eight rounds (of waves). Even without the Bee, with the right elements, the Sand Hawk is a nice, quick way to unleash a volley of pain against a specific enemy.
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. The Sand Hawk, the 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.
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.
Unkempt Harold 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. With even moderate anarchy, Gaige turns any boss into a joke so long as it's not of the Only-weak-point-takes-damage variety.
A combo that can obliterate anything other than raid bosses with 2 seconds of firing (that includes lvl 52 super badasses) is the Infinity (high fire rate pistol with infinite ammo and no need to reload), the aforementioned Bee shield, and the Sheriff'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 the Infinity. With the right set-up, this can lead to doing over 100k damage per shot.
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 if they ricochet off a non-enemy. Because the extra projectiles doesn't get listed in the card, each projectile still gets the Bee amp bonus. The ricochet Fibber works wonders for Gaige, as the extra pellets get the homing effect from her Close Enough skill without the associated damage penalty.
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.
Assault on Dragon Keep brings us the Grog Nozzle, which does about a fifth of the damage of comparable weapons, but grants health regeneration 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 or reload, 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 the single 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. 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 as the Norfleet fires three energy balls compared to Badaboom's six rockets.
The Badaboom is an often-sought weapon in its own right. Badaboom fires six rockets at the cost of 1 ammo and when spawned with the parts that will achieve the highest damage possible (Torgue exhaust and grip along with the extra damage accessory), it is actually the second most powerful launcher in the game in terms of total damage per shot after the Norfleet, which makes it an excellent all-around launcher as its powerful and ammo-efficient. A low-level one is still going to be useful for purposes such as rocket ammo restoration and Rocket Jump for Sequence Breaking purposes. Its also much easier to farm than the Norfleet and the Topneaa as the Badaboom is farmable from a rare spawn enemy (King Mong) instead of a raid boss (Norfleet) or chests (Topneaa). With the Norfleet being a Maliwan weapon, the Badaboom is considered the best explosive Rocket Launcher available.
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.
Also from the Tiny Tina's DLC "spells", there's the Chain Lightning that can be dropped from Badass Sorcerers. Chain Lightning fires a bolt of lightning that explodes upon impact with a solid object or upon certain distance, and as the name indicates, it can chain to multiple enemies. As the explosion is almost instantaneous, it makes the Chain Lightning a perfect grenade for regaining health with Moxxi weapons as the damage by Chain Lightning can shot your health back from near-death to full in a near-instant.
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).
After a patch that heavily buffed its statistics, the legendary Fastball grenade is turned from a Scrappy Weapon to one of the best grenades in the game. The Fastball has massively increased damage and faster travel speed, but the blast radius is so small, it's practically becoming a grenade that you must score a direct hit with. It also fires as if it's a baseball. What makes the Fastball so strong is its insane damage output: A perfect Fastball statistically is the most damaging weapon per projectile in the game and the second most damaging weapon overall, behind only the Norfleet. While the unique firing properties makes it hard to use at first, once you got used to how the Fastball fires, the Fastball becomes a grenade that can one-shot many enemies thanks to its massive damage output.
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. At the very least, it's an effective way to destroy Crystalisks, given their large, obvious weak spots. This, along with moral reasons, is why it's good to stay true to Una Baha for her quest over Hyperion's blatantly shady offer, which nets a Joke Weapon in its place.
Believe it or not, the highest-DPS weapon in the game is actually the Pimpernel, a blue-quality 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. The main source of its power? When the bullet collides with terrain or an enemy, it splits into five, making it excellent with the Bee.
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 thanks to the Gunzerking skill. Good examples are the following:
Grog Nozzle, with its mechanics 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.
Anarchy + Close Enough = Massive amounts of damage even when you're only making your shots ricochet. What makes this truly ridiculous is that despite 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 at rank 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 the ricochet barrel. 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.
With the release of the Commander Lilith DLC, it is discovered that the Hot Mama sniper rifle from said DLC have perfect accuracy when scoped in... even with Gaige on max Anarchy stacks. The usage of Hot Mama makes shooting enemies from long range now a viable option for Gaige even with max Anarchy stacks. Its only limitation comes from the fact that Hot Mama came in fire element only, but considering Anarchy boosts damage massively and you can now land critical hits reliably...
There's also Gaige with the Veruc. Although a Dahl rifle seems like a weird choice for an Anarchy build, the Veruc has an excellent pellet spread that can hit all three critical spots of a Loader at once - arms and eye - and combining it with Close Enough turns the assault rifle into a close-quarters killing machine. Fire in the general direction of a crowd of enemies, and if the actual burst doesn't get them, the spread of the bullets zipping around will. The Veruc is also accurate enough to be a very viable weapon if on low Anarchy stacks, allowing an Anarchy-focused Gaige to pick off enemies at long and medium range.
Using class mods to heavily increase points in the Smaller, Lighter, Faster skill (improved reload speed at the cost of clip size) and carrying a Jakobs Shotgun (great damage and fire rate, solid accuracy and reload, small clip size) allows Gaige to reload so quick that it doesn't take time at all, basically making a shotgun version of Infinity. That gives an Anarchy stack for each shot. It's so powerful it can kill the Warrior before it even has a chance to dive into the lava.
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.
Deathtrap is also insanely powerful thanks to the Best Friends Forever skill tree. Among the powers it grants are Upshot Robot, an ability that extends Deathtrap's duration and increases melee damage for each kill; Explosive Clap, a special ability that can wipe out entire groups of enemies instantly; and Sharing Is Caring, which gives Deathtrap a copy of your shield on top of his already incredible health. Oh, and Deathtrap can levitate and move through walls, and can shoot lightning bolts at flying enemies. With proper specs, Deathtrap can easily trivialize any non-boss.
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.
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 OP8 with the Avenger and a Bee in three seconds. You heard us. Three seconds.
Take the Assault Rifle, explosive, and gun damage boosts from Torgue Assault Rifles, and then slap electric damage on top of that. You get the Peak Opener.
The Vladof Sniper Rifle Droog becomes this with Salvador, who rapidly generates ammo while gunzerking and can possibly pick up Ammo Regen as a perk for his class mods. As Droogs have above-average magazine sizes and fire rates for sniper rifles, 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 regeneration 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. And that's before mentioning that because Lyuda's extra projectiles aren't listed on the item card, all of the extra projectiles would receive the full amp bonus from The Bee, giving the weapon even more damage.
Low-level Droogs are equally monstrous in the hands of Zero, who can use their high fire rate and stability to rack up massive Critical Ascension stacks before switching to a damaging sniper rifle and proceeding to blow everything in sight to pieces.
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.
Maya's Chain Reaction skill can produce similar effects, although it's harder to get going. Even boosted to 11 points with a Trickster class mod, she can only get the ricochet chance up to 88%, and it only works while an enemy is trapped by her Phaselock. That said, when everything does align properly, the results are spectacular, to the point where the game itself starts struggling because of all the hitbox collisions.
Fastball grenades, which lack an explosion radius but make up for it with crazy damage output if you hit the target, can be game-breaking in hands of Maya/Salvador/Krieg. For Maya, Phaselock an enemy (or a group of enemies if you learned Converge), which will pull them out of cover and making them immobile, throw a Fastball, boom, gone. For Salvador, he has a skill that allows you to fire two grenades at once at the cost of one during Gunzerking, essentially giving you free double damage upon scoring a hit with it. For Krieg, the Fastball is the perfect grenade for chaining Bloodsplosion for reasons mentioned above. Minibosses (and even some raid bosses for Krieg) don't stand a chance.
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 Gunzerking skill Money Shot gives a huge damage boost to the last bullet in the magazine. Pair it with Inconceivable, which gives all of Salvador's shots a chance to not consume ammo, and 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?
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.
With the right combination of skills and relics/mods to grant him buffs with sniper rifles Zer0 can easily be turned into a long range killing machine that does insane damage with critical hits. At high enough levels (let's say by level 30) he can drop most non-badass enemies in 1-2 shots while chewing up bosses with sustained and well aimed fire to weak points. He's not quite as broken as Mordecai was in the first game with his ability to ignore shields and regenerate health from kills but still pretty close.
Deputy Sal, a build with Salvador that involves your main (right) hand wielding a Grog/Lady Fist and the off (left) hand wielding a Jakobs shotgun that can shot twice at minimum (Rustler's Orphan Maker or Quad, with a grip that can make the gun fire twice (Jakobs or Bandit), are usually the go-to choice for this build). Normally, Jakobs shotguns dont benefit as much from Money Shot due to their small mag size... But when using Gunzerking, if you put the Jakobs shotgun in your off-hand, it can receive the full Money Shot bonus as the game actually only looks at the main hand guns magazine size to calculate the Money Shot bonus for BOTH GUNS. Its other key advantage lies on the fact that its a Jakobs weapon: Low mag, combined with its fire rate is only limited by how fast the player can click/tap the fire weapon button, means that you can chain Money Shot bonuses every two shots in very quick succession. Now combined this with the Grog (for healing) and the Lady Fist (for critical hit bonuses) and a Class Mod that gives you an extra five/six points on Money Shot, and you will have a build that will melt almost all enemies in Pandora. Unlike the DPUH/Grog build, this build is also viable for flying enemies as you don't need to worry much about Harold's slow projectile speed when fighting airborne enemies.
Maya's Cloud Kill skill causes a corrosive area of effect damage around any enemy she shoots. Originally, it was rather lackluster, not really doing enough damage to be worth it. However, it was buffed by almost four thousand percent in a patch. Now it can take down any non-boss enemy in seconds, including badasses. It's especially effective against Hyperion robots; being armored enemies, they take extra damage from corrosion, and they make up the majority of the enemies you'll be fighting in late game. It's also excellent for getting Second Winds, since you only have to land a single shot on an enemy and let the cloud finish them off for you.
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 the 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 that will make the Fibber deal the amount of damage that it says on the card, meaning that a level 20 fibber could potentially deal the same damage as an ordinary level 45 Hyperion pistol.
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.
In Mister Torgue's Campaign of Carnage, there is a set of racing side quests, the last of which is level 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.
It is also possible, with a few players by your side, to drive multiple cars in anticipation of crossing these checkpoints. With two players on opposite ends of the track repeating the course, it makes completing this race far easier.
Zer0's "Rising Sh0t" ability gains a stack (up to 5 legitimately) when you shoot a target resulting in a bonus of 10-22% extra gun damage and 9-19.8% extra melee damage per stack. Due to an oversight, however, these stacks will stay "indefinitely" (it only resets when you quit the current game session) if you were to reset your skill point allocation while you still had those stacks. Ultimately a player could repeat the process of building up 5 stacks then resetting to constantly build up that flat damage boost to 999 stacks (resulting in a 9990-21978% gun damage boost and a 8991-19780.2% melee damage boost) as long as they had the money, ammo and time to setup.
The Morning Star Sniper rifle is a quest reward item that upon scoring a critical hit, Adds 20% critical hit damage as a stack for a short time similar to Zero's Critical Ascension skill. If you empty the Morning Star sniper rifle, then repeatedly swap weapons over and over and over again, you can both transfer the properties of the Morning Star onto other weapons and multiply the number of stacks you get after each critical hit. This can be done infinitely, and only resets upon exiting the game. with this, you can shred basically every enemy to pieces no matter which character you're using. The only downside is the Nagging voice is also multiplied.