Boomer

The Boomer is a Special Infected (playable in Versus Mode) that vomits on the survivors to attract the horde to them, It's easily killed but it´s dangerous to do it in close range because it explodes and covers with bile whoever is close to them.

Like other infected, it warns the players when it´s approaching by doing sounds, it´s slow and weak. When it vomits on someone, his or her halo turns purple and blinds out.