It is the removed arm cannon of a guardian drone. It fires a ball of energy that acts as a grenade, bouncing and then exploding after a period of about 3 seconds. The projectile has the ability to move buses and cars before exploding. This weapon is difficult to use at first, but becomes an extremely devastating weapon after learning how the orbs arc.
Hitting a target's mid-upper body with the ball of energy will usually result in the ball dropping straight down before exploding, making it a good way to hit specific targets with the explosion. When fired into water, the projectile will continue normally, bouncing off any obstructions under the water. It will explode normally like other explosives.
The drone cannon can fire 417 orbs before breaking.
Drone cannon Ex-BMothership Zeta, a unique variant whereupon the ammunition explodes upon impact rather than bouncing around.
PCPlayStation 3Xbox 360 When taking the cannon from a drone, it has no icon (PipOS Error - 26 [File Not Found]). This is not necessarily a bug and could in fact have been included deliberately, due to the weapon's alien origins and the 'PipOS' not able to recognize it.
PCPlayStation 3Xbox 360 When examining a cannon dropped by a drone in the normal worldview (not by searching the drone's inventory), it will always show a value of 999 caps (app. half CND) regardless of the weapon's actual quality. This could also not be a bug and be deliberate, since the 'PipOS' not recognizing it and giving it a default value in caps.
Xbox 360 If you equip a drone cannon while wearing Tesla armor, the coils on the back of the chest piece will dissapear.