Alien
The Thing (1982)
Carrie (original)
Psycho (1960)
The Day of the Triffids (any)
Invasion of the Body Snatchers (forget the year; the one with Donald Sutherland and Leonard Nimoy, anyway)
Village of the Damned (either/any)
Hallowe'en (original)
The Fog (original)
The Woman in Black (either)
Dr Terror's House of Horrors
Horror Express
The last couple probably fall into the 'So bad they're good' category, but that's Hammer for you.

Listed like that, most of them are clearly 'old-style' horror, where it's no so much what you do see as what you don't. I think that's where horror works best.
Modern horror...generally, it's not subtle. There's little suspense, so they either go for the gross-out or they use the old low trick of using a long shot and silence before having something flash by close to the camera, accompanied by a high, sharp note played
loud. IMO, it rarely works and, in my case, merely annoys. (Actually, it makes me angry, to the point where if the producer, writer or director was sitting next to me, they'd be apt to get a smack in the face. Call it reflex. As it is, I simply mutter something along the lines of 'Oh for [slang term for sex]'s sake'...usually in unison with my gf, who takes that attitude to horror in general.)
Torture porn...nope, stuff it where the sun don't shine. I don't even consider it to be horror in the traditional/genuine sense.