The Thing - I love the original but John Carpenter's version is absolutely awesome. The special effects by Rob Bottin are incredible.
It - A group of friends who grew up together reunite to battle an evil clown. What's not to like.
Alien - I love them all, especially Aliens, but the original took horror/scifi to a new level.
An American Werewolf in London - A great horror/comedy. The werewolf transformation designed by Rick Baker is astounding.
Salem's Lot - I remember watching it with friends when it first came on tv. It scared us all.
The Lost Boys - A bit dated but still a pretty cool movie. I loved the punk rock vamps and the rock soundtrack.
Shaun of the Dead - A masterpiece of British comedic genius.
Fido - Another funny film about a boy and his zombie.
Dawn of the Dead - Zombies in a mall. Again, what's not to like. I love the original and the remake.
Altered States - This is one freaky, weird movie but it's freaky, weird good.
The Frighteners - A transitional film for Peter Jackson. Based on this film alone I knew he could tackle Lord of the Rings and do it justice.
Fright Night - This one may be my favorite vampire film of all time. Roddy McDowell is spectacular.
Identity - A fantastic use of the "10 Little Indians" murder plot.
Ghost Ship - Not much to say about this flick. I just like it.
Blade - An incredible blending of the horror/action genres. Some of the effects are similar to the Matrix but Blade came out a year before Matrix.
Silence of the Lambs - How can you not love Anthony Hopkins performance as Hannibal Lecter? No one can touch it.
Dracula - The Frank Langella version from the 70's is still the best one so far.
From Dusk 'Til Dawn - What starts out as a typically wonderful Tarantino/Rodriguez crime film morphs into an over-the-top vampire blood bath featuring Harvey Keitel as a Baptist minister who's lost his faith but must regain it to fight off the bloodsuckers. And Clooney's never been better in my opinion. And it has Salma Hayek in it. Say it with me...what's not to like?
The Mist - This is a new favorite. I love Darabont's work and I think he did a great job with this one but I hate his ending. It was a bold choice but he should have just stuck with King's ending.
I'm sure there are more but this is all I can think of right now. What are some of your faves?