Zapinator

The Zapinator was a weapon that was accidentally left in the game when released, but taken out in a subsequent update. It resembled an NES-era light gun and shot very rapidly, dealing 50 damage per hit - around 500 damage a second.

Contrary to popular belief, it is possible to obtain the item in game by modding the game, however a current method has not been released publicly, due to fear of the method being patched.