Also, the original "When A Stranger Calls.." from 1979.. the entire movie was good. There's a scene later in the movie with the killer - Kurt Duncan, it's one of the best scenes in the movie, he's standing in front of the mirror, and he breaks down - showing him coming to terms with how remarkably insane he truly is..
"The Entity" Probably takes the cake in terms of scaring the every-living honeysuckle out of me. I saw it for the 1st time - alone and like 2-3AM - as a teenager, I didn't sleep until the next day after my dad came home from work. The trailer doesn't do it justice, at all.
Also, "In The Mouth Of Madness" a fantastic movie, that has a lot of truth in it in terms of propaganda, and extremely well played by Sam Neill - the ending scene where his laughter turns into horrifying tears.. gets me every time. The message behind the movie was very well-done.