Y'know, I watch a lot of horror movies on general principle and I enjoy them, but I rarely find them sticking with me. They're here and gone and I rarely think of them again.
If I had to pick a movie that genuinely creeped me right the heck out, I'd have to go with "They." Something about that final scene, with her pounding on the 'wall,' just sticks right in my head and won't go away. I've seen a lot of the old classics of the genre, and none of them have unnerved me in quite the same way.
In terms of movies that actually horrified me but that I deeply enjoyed, I'd toss out "Lord of War" and "A History of Violence." The feeling I get from them is more of an intellectual sadness and a cold despair rather than fear, but they were hard going down. (I'm particularly fond of the ending of "Lord of War," which is predictable and preachy and still just perfectly on the money. The opening
credits are more familiar, but also enjoyably sadistic.
However, my
favorite horror movie will always be "Tremors." I think they hit the perfect blend of enjoyable characters, jump-scares, building suspense, humor, and moments of real fear. The sequels should be set on fire, mind you, but the first movie is just grand, in my opinion.