I'm a big fan of horror films!
My absolute favorite is Silence of the Lambs. The scenes with Catherine in the well are bone chilling.
The original Halloween is so elegant and efficient. Michael sitting up at the end is one of the most effective flights I've seen.
The original Texas Chainsaw Massacre is the closest thing I've seen to a nightmare. It feels so realistic and claustrophobic. Very clever satire as well.
Warner Herzogs Nosferatu is very spooky (largely thanks to Klaus Kinski, one of the biggest creeps in film), and feels very relevant today. The ending is incredibly bleak.
The original Black Christmas is super spooky and suspenseful, and might be the smartest slasher movie. A great cast of smart, funny character, who act exactly as they should. Margot Kidder steals the show, but Olivia Hussey is great as the independent girl who breaks it to her boyfriend that she's going to get an abortion.
Finally, of all the Hammer horror films I've seen Mt favorite is The Mummy. Peter Cushing and Christopher Lee are awesome, and the story is the perfect distillation of the (mostly lousy) Universal Mummy movies from the 40s. It's really everything you could want from a Hammer horror, it's the one that best lives up to the studios reputation.