The Amityville Horror with Ryan Reynolds
I watched that in the dark in my basement all alone when I was like 14. I think that's the most frightened I've ever been watching a movie. And I don't get scared easily...
Insidious 1 had me freaking out for two months. The scene with the red face had me having a meltdown. And the ghost lady at the end had me flipping out and scared to look in mirrors.