The Witch, from what I saw, was very frightening to me. It must have been the witch's cackling that got to me.
Funny how things that scare some people don't scare others. The Ring was not scary to me, but Blair Witch did. A friend of mine said The Ring was soooo scary, but I didn't think anything of it. The Conjuring-- same thing. And that was based on true events.
The Exorcist's story changed to prevent anyone from knowing who the parent was. It was a male instead of a female, with a famous father. A friend of mine I grew up with, says a girl at her stay away camp became possessed. This friend wouldn't see that film for that reason.