In Borderlands 2, It is obtained randomly from any suitable loot source, but has an increased chance to drop from The Warrior located in Vault of the Warrior and the Handsome Sorcerer located in Dragon Keep. In the Mr. Torgue's Campaign of Carnage DLC, it may be available at any Torgue vending machine as the Item of the Day.
In Borderlands: The Pre-Sequel, the Flakker is obtained randomly from any suitable loot source, but has an increased chance to drop from Even-More-Disgusting Tork located in Stanton's Liver.

Special Weapon Effects

Flak the world. – Fires several invisible projectiles that detonate shortly after, causing 6 explosions each. Increased damage and projectile splash radius. Greatly reduced fire rate, projectile velocity, pellet count, and accuracy.

Usage & Description

The Flakker is a crowd-control weapon. It causes huge damage across a wide radius but is challenging to apply in common combat. It only causes damage on detonation, which gives the Flakker a limited range in two ways: the target cannot be too close, or too far. It is very hard to hit a close target, as the rounds fly away; for this reason, other shotguns are more effective in practice.

The Flakker has a very low fire rate, making it unsuitable at times. While cocking the gun, characters will be vulnerable as they cannot sprint and avoid incoming fire. The Flakker can be fired much faster by switching weapons as soon as it is fired and immediately switching back to the Flakker, or if Salvador's Keep Firing... is active. This negates its poor fire rate as well as allows the character to sprint between shots, significantly increasing its effectiveness at close range. The high-spread nature of this gun, coupled with the explosive effect, makes it effective against flying enemies within range, as the huge coverage area can help catch swooping targets. Similarly, enemies with large hitboxes can also take tremendous damage from each volley.

A useful method of using this weapon effectively is to fire it from above smaller enemies at their knees. The projectiles often ricochet off the ground, allowing a better chance of damaging the enemy.

Notes

• As mentioned before, each Flakker pellet causes 6 explosions. Two of them have a small AoE, two medium and two large. The large explosions deal 120% card damage, whereas the rest deal 100%.
• Pairing the Flakker with Zer0's Rising Sh0t skill can be devastating, since it allows him to gain maximum stacks in a single shot and its low fire rate allows stacks to be retained for a longer period.
• The Flakker was a guaranteed drop from The Warrior during the Borderlands 2 $100,000 Loot Hunt, on Day 30. A hotfix on that day increased the explosion radius of the Flakker.
  • As the Flakker was programmed as an extra loot drop, it was possible for The Warrior to drop two Flakkers or another legendary within the loot pool in a single encounter.
• As the detonation of the Flakker's projectiles based on time and not distance, Zer0's Velocity or Maya's Accelerate can greatly increase the range and spread of the projectiles, making the Flakker useful for distant enemies at the cost of rendering close-quarters combat impossible with it.
• Firing the weapon and then quickly switching to a launcher can greatly increase the damage of the explosions caused by the projectiles. This abuses the passive weapon effects glitch to apply the base damage of the launcher to the explosions currently in the air.
• The Flakker's pellets can land critical hits. While it can spawn with the critical hit accessory ("Juicy" prefix), its low accuracy makes it next to impossible. As a result, Salvador's Money Shot has little effect on Flakker, and while Claptrap's One Last Thing does benefit, the bonus effectively only triggers on the second-to-last shot.
• The pellets' splash are considered explosive and bullet damage, but not grenade damage. It cannot activate Krieg's Blood Bath skill, but works with Maya's Reaper skill.
• With the "right" parts, a Casual Flakker may have superior base damage at the cost of such a low accuracy that the its card reads a negative value (see image above).

Trivia

• The "+100% Weapon Fire Rate." is an indirect emphasis on its slow fire rate.
• "Flak" comes from the German word "Flugzeugabwehrkanone", literally meaning "aircraft defense cannon." Since the First World War, it has been used as a generic term for both anti-aircraft guns and the rounds they fire.
• The flavor text is a reference to the word Frak from Battlestar Galactica, as in "Frak The World".
• In the mission Grandma Flexington's Story: Raid Difficulty, Grandma Flexington mentions the Flakker to be a hated weapon.