Ah Suspiria.  Classy and nasty at the same time.  Not quite up there with my top choices but real close to the top nonetheless.  I never got around to the last in his loose trilogy of films... I'll have to correct that at some point.

Aliens.

I love horror movies, my favorites are: Dawn of the dead, [REC], the exorcist, and 28 days later.

paranormal activity 2 was great. I really got a nightmare and im 18 lol...oh well, cant shake off the weird noises at night lol

Well, my favorite is definitely Poltergeist (the first one only).  Not that scary, just a great movie.

I also like Psycho, Halloween and A Nightmare on Elm Street; the originals only, NOT any of the sequels (Dream Warriors was ok) or any of the recent terrible remakes, and of course, the Shining.

But the movie that scared me the most when I was a kid?  Probably an old '78 movie called The Manitou about Native American black magic.

In no order

[REC] (Spanish version
Battle Royale (not sure if this constitutes horror ...)
The Shining
Funny Games U.S
28 Days/Weeks later
Candy Man 1/2
Texas Chainsaw Massacre (Original and remake)
The Hills have Eyes
The Host
Children of the Corn
IT (childhood fav!)
Scream trilogy
Nightmare on Elm Street
The Mist
The Ring 1/2