Absolute Force Online is a Free-2-Play FPS developed by TQ Digital. As well as most normal competative FPS modes there is also a zombie mode. In this mode most of the players start off as human while a few spawn as zombies. Each zombie has a special ability, and killing a human will turn that player into another zombie. The Bloody Nurse zombie has a cloaking ability. Currently in Beta is an additional monster type for zombie mode: the Vampire.
Vampire
Bloody Nurse