Left 4 Dead 2

The special zombie encouraged players to keep moving and keep there head on a swivel. The zombies also encouraged the player to not  leave your teammates. By staying near your teammates you can get healed and saved if you are getting attacked. If i was a spitter i would  counteract the players ability and spit on them. From that my fellow zombies would attack the players when they are spit on. The acid would also damage the player which will make it easier to kill them. Now if i was a jockey i would jump  on the players back and move them into a group of zombies.