1. The Blair Witch Project - An ingeniously simple concept (three teens get lost in the woods while chasing a witch legend) spoiled by hype that made it impossible for the film to ever live up to its reputation. The scares here come from what isn't seen, such as the main characters fleeing into the dark woods surrounded by mysterious noises that may be chasing them.
2. Night of the Living Dead - The grainy rawness of director George Romero's low budget approach makes it all the more terrifying as a group of strangers huddle in an isolated farmhouse to escape the army of undead outside. A watershed film that spawned an entire sub-genre of pop culture (see #6 below).
3. The Ring - Usually Hollywood can't be trusted to remake a foreign film, but this is the exception. Exporting a strange "J-horror" premise (you die seven days after seeing a weird haunted videotape) gives the film an unexpected freshness that makes it impossible to predict how it's all going to turn out. The weird music is just the cherry on the cake.
4. The Omen (1976 original) - Many prefer that other tale of superatural childhood evil, The Exorcist, but that movie's too intellectual and, frankly, rather boring in the first half. It's like sour medicine: you know it's good for you, but it's not that much fun. The Omen, however, is the tasty junk food, delivering big scares start to finish.
5. The Others - Many lumped this in with The Sixth Sense because of the fashionable Big Twist Ending That Changes Everything, but this is a much scarier, much creepier movie because of the old-school Gothic ghost story elements: the rambling house full of shadows and lanterns, the question of what's real and what isn't (including the sanity of a brittle Nicole Kidman). Good stuff.
6. Dawn of the Dead (2004 remake) - A peerless updating of the zombie genre. A bigger budget allows for more action, better zombie effects, and a better cast (yes, Ving Rhames is always good, but the revelation here is Jake Weber). Director Zach Snyder stuck to the Romero playbook...
7. 28 Days Later - ...while director Danny Boyle reimagined the Romero template by making the monsters "infected" rather than "undead" and, of course, by making them sprint like terrifying Olympic relay runners. Points must be deducted for a muddled and anticlimactic third act, but the first hour is so strong and scary that we can overlook any shortfalls.
8. Hostel - Unfairly labeled as worthless "torture porn," this does what any good horror film does: take society's fears to the extreme. Here we get a murky Internet rumor come to life as our hapless characters stumble onto an Eastern European black market snuff ring. It's scary because you imagine such a thing is possible.
9. The Shining - The cold dread of this movie, filling the empty rooms of the massive Overlook Hotel, is almost palpable. So many of the small touches can still give one goosebumps, such as little Danny Torrance suddenly seeing the ghosts of two dead twin girls. The Cheese Fry is freaked out just typing that.
10. Texas Chainsaw Massacre (the 1974 original) - Like #2, the cheap grit of this low-budget film gives everything a sweaty newsreel immediacy (i.e. "oh my god, this is really happening"). And because it's filled with unknown faces, you have no one of predicting who - if anyone - will survive. The godfather of the many teen slasher movies (FYI, the best of the 1980s: Friday the 13th: The Final Chapter, the quintessential slasher movie).