Every year I tell my wife that I want to try to watch one scary movie a day during the month of October, but I never manage. I'm going to give it a shot again this year. Some of my faves though are Halloween (Carpenter's original, duh), The Thing (Carpenter again), The Fog (also Carpenter...), Nightmare on Elm Street, House, Lost Boys, Monster Squad, The Shining (Kubrick's), Ghostbusters, Poltergeist, Friday the 13th, Charlie Brown & The Great Pumpkin, etc. I try to watch a good mix of horror & whimsical.
I also enjoy Halloween III, even though it doesn't have the greatest reputation - there's just something about the mood of the movie that I really like.