I like ex-humans, the ones Shanks referred to as monsters. Vampires, werewolves and zombies all have terrifying potential, especially ina movie, because if the marketing people are good enough to hide that they are in the movie before its release, it can be quite an unhappy surprise when you find out an apparently normal person is really a creature. The wole hidden terror/loss of humanity thing is wonderfully effective.
if nothing else, read the first page of father dillon's funeral,
http://scaredyet.net/lit/shamb.aspx
I used that technique in the beginning.