AA12

How To Obtain
Get to Level 45, then you can equip it in your Primary Slot.

Trivia

 * 1) It is the first fully automatic shotgun in the game.
 * 2) It is the only gun in the game with a drum magazine attached to it.
 * 3) It is the last Primary Weapon one can unlock before unlocking The Minigun
 * 4) It is the last shotgun unlocked, after the AA12 there are no more shotguns.