Well, I was about to start a series of articles on my all time favorite movies, but I guess I can spill some of them here. (And I'll try not to repeat any that have already been mentioned. If I do, it was an accident.)
The Uninvited (1944) -- Good Ghost v. Evil Ghost over young girl.
Phantasm (1979 Original only) -- One of the scariest, most original horror films ever. What is that Tall Man out at the mortuary really up to?
The Haunting (1963) -- Forget the remake, they had no grasp of the story.
The Legend of Hell House (1973) -- Same author as Stir of Echoes.
Friday the 13th (1980) -- Great movie. The low budget and poor acting just make it seem even more realistic. Pre-Jason and his machete
The Thing (1982) -- John Carpenter goes back to the original story and directs the hell out of it.
The Fog (1980) -- Don't betray a bunch of evil pirates when John Carpenter is around.
Jaws (1975) -- You'll never look at the water the same way.
The Wicker Man (1973) -- Not one of my favorites, but a truly creepy and bizarre film about the disappearance of a girl in a pagan enclave on a Scottish island. Considered a minor classic.
Also just about any film from Hammer Studios during the 1960's but especially if they have Peter Cushing.
Most British anthology horror films, where they have multiple stories loosely tied together. I love those. (Special points if they were written by Robert Bloch or, again, feature Peter Cushing.) eg, Tales from the Crypt I (1972) & II (1973) -- II is sometimes called The Vault of Horror (1973).
If you really want freaky, the horror films of David Cronenberg (director of the aforementioned Scanners). (Try Videodrome (1983) or The Brood (1979).)
And if you want the most intense, pure horror put on film check out an Italian zombie or demon movie sometime (see Dario Argento of the aforementioned Suspiria).
You've whet my appetite. I think I'll go watch some of those now myself.