History of Rampage

Rampage is a weapon trait: each kill with the weapon temporarily increases its damage, stacking up to three times. Reported values are roughly +10%, +21% and +33% at one, two and three stacks. Sources differ on the stack timer details (3.5 versus 4.5 seconds), so check in-game. It appears on weapons in Onslaught such as the Void machine gun Hammerhead.