Great topic, Adip.
10 favorites in no particular order of preference:
1. The Innocents: Terrific horror with not a single drop of blood spilled. A young woman shows up as a governess on an ancient British estate to find that there's something very very wrong with the kids she's supposed to be looking after.
2. The Texas Chainsaw Massacre: The Tobe Hooper original is one of my favourite films of all time. No self conscious bullshit, no action star heroics and some of the most original art direction and a genuinely psychotic vibe that's never been duplicated.
3. Red Rose: The best Indian horror film ever made. Rajesh Khanna as an aging creepy serial killer with a family that makes the people in TCM seem quite affable and well adjusted.
4. Carnival of Souls: One of the if not THE first 'weird shit happens' films. After a traumatic car crash, a young woman moves to a small town to take up a job as the organ player in the church only to find she's being haunted and is drawn for some inexplicable reason to an abandoned fairground on the outskirts of town.
5. Night/Dawn/Day of the Dead: The best zombie films ever made. Didn't care much for Romero's attempts at tagging on to the story (Land of the Dead) or franchise rebooting (Diaryeah of the Dead), but nothing can take away from the genius of the original trilogy.
6. The Beyond: Bizarre, a little silly and ultraviolent. It makes a LOT more sense than people would have you believe, though.
7. Demons: Anyone who has seen Evil Dead is going to love this film. Absolutely mad plot that has people turning into demons (duh!) driven by a kickass soundtrack featuring Accept and Motley Crue.
8. Evil Dead 1 and 2 - didn't care too much for 3.
9. The Shining
10. Santa Sangre: A surreal and oddly poignant slasher film. EAsily Alexandro Jodorowsky's best film.