Strange walking, heat-seeking grenades. They're great in swarms, but a skilled player can easily avoid them. It's not full screen, so you have a chance to avoid incoming fire, and it's more accurate than even the locked-on Eightball rocket launcher. It's more controllable over long distances, but you're an easy target since you can't see what's around you. The Minigun with a cooler model.
Primary fire spits bullets out at an extremely fast rate, and alternate fire is even faster.
The Zapper bears some resemblance to the Quake weapon of the same name. Primary fire has a tesla coil effect, shocking anyone in range with a bolt of electricity. Alternate fire charges up for a few seconds, and then lets loose a more powerful bolt. The flint-lock style shotgun, one of the better looking weapons in the new pack. The new Zapper.