The Plunger is the Rabbids mainly used object. It has been used in about every game in the series.
In the first game, Rayman used the plunger to shoot the Rabbids in the FPS mini-games. The Rabbids also appeared using the same gun as Rayman to shoot at him.
In the second game, the plungers are used in the FPS mini-games again being used the same way. Each player has a colored plunger to tell who shot the plunger. Apparently, the gun in this game has a shorter amount of plungers and the ammo meter appears on the pointer.