Something Wild was one of the first movies that completely unhinged my expectations. For the first hour, it's a wacky slapstick 80s flick (with the Feelies! Heck yeah), but it changes tones significantly towards the end. That said, I've only sat through once since I first saw it as a teenager and even that was over a decade ago.
Movies on the list that I haven't seen are The Poltergeist, The Omen, The Texas Chainsaw Massacre, Rosemary's Baby, The Thing (John Carpenter verision), The Evil Dead, An American Werewolf in London, Henry: Portrait of a Serial Killer, Lost Highway, and The Hitcher.
My wife and I watched American Werewolf in London the other night. That's another movie I watched as a teenager and not since, but it's aged remarkably well. It's not very suspenseful, but the visceral horror of his literal transformation into a wolf is wretchedly naturalistic. Rosemary's Baby is just plain creepy. It was on the other night, too, but since my wife is pregnant, we skipped it. Lessee, I remember Poltergeist as scary when I was younger, but I don't know if I'd feel the same way now. The Omen was just kinda silly. The original Texas Chainsaw Massacre is very creepy, partially because it was shot so cheaply that it seems like a documentary at times. The John Carpenter version of The Thing is just kinda disgusting, but occasionally suspenseful. Skip The Evil Dead in favor of the far superior Evil Dead II (which leads directly into Army of Darkness). Henry: Portrait etc. is almost more of an art-psychology movie than a horror flick. I hated it, much as I hated Man Bites Dog. That kind of nihilism isn't scary to me so much as just plain sick. Lost Highway is David Lynch's worst film and I wouldn't call it horror. In fact, it horrified me much less than, say, Mulholland Drive or Blue Velvet. I haven't watched The Hitcher since I was a teenager, but I remember it to be one of those cheesy "omnipotent serial killer" movies where Rutger Hauer could somehow predict every move C. Thomas Howell made. Probably good for late-night cable, but don't waste your money on it.
What else was on the list?