I'm something of a nightmare fetishist and don't really get freaked out by much, at least not anymore. But if I had to pick something, it would probably be Frank Booth from Blue Velvet. The more I see that movie, the more horrified I am at the possibility that someone like him could actually exist and potentially have as much power as he does, even if he is only a creation of David Lynch's imagination. Every time he's on screen, you know that absolutely nothing good will come of it and that he is someone to be utterly terrified of, especially once he whips out that nitrous tank... *shudder*