I love them, and I've seen very few. Recommendations, anyone? The more pants-shittingly scary, the better. I haven't been really scared by a movie since the first horror movie I saw (Ringu, for the curious). I want shit that will haunt me and give me nightmares like Sadako and her fucking fingernails as they came out of the TV.
Note: I haven't seen Ringu since. I have no idea if the scene would still get me like it did when I first saw it. I hope to got I'm not completely desensitized to things like that.
This is brought on by my just having seen Diary of the Dead in theaters. I hear it isn't Romero's best, and if that's true, I can't wait to see more of his work. I'll be renting the rest of the Dead series as soon as I have time to watch them.
Don't fail me /tv/.
My favourite is The Shining (Kubrick's movie version.) I'm also fond of Ringu and Ju-on. Everything else I have either rated average or not seen.
The Exorcist.
I haven't seen anything that can compare, but then again I haven't seen much.
I like Kairo. If you haven't seen many other J-horror movies, or other horror movies with a similar style, it should be pretty scary. I also found watching it on a computer made certain parts feel creepier. And as added bonus, on top of the horror, it's really depressing.
Another one I'd recomend is A Tale of Two Sisters. It's made of win and creepiness, although towards the end it shifts more towards general drama. (Actually, I haven't seen it in forever, so maybe it's more mixed up, but it certainly has a lot that's not so much pure horror.)
"Saw" There are eight of them since 2004. Must see if you like to pants-shit.