Zombies are the ultimate monster. Unlike Vampires, Werewolves and Ghosts, they lack exploitable weaknesses or definable goals.
They just keep coming with an implacable hunger for your flesh, and the only way to stop a zombie is to inflict enough damage that it is unable to pose an effective threat.
Unfortunately, by the time you've put one down, a dozen of his buddies will be scooping out your brainpan like a bucket of Ben and Jerry's.
The mindless hungry dead. God I love 'em.
[Okay...technically they would be Ghouls...but you get my drift]