The Gauntlet Plasma Bolt is a small plasma caster built into the Predator's gauntlet. The Predator uses this weapon in the meat locker in Predator 2 and fires off a powerful rocket from his wrist which hits Harrigan. The Predator used this after its shoulder cannon was destroyed which suggests the wrist gun is simply a backup weapon; the fact that it only appears to be able to fire once supports this concept.