As a complete experience it isn't too scary but some scenes just caught me off guard... Especially the ending. Screw that ending.
Art of the Devil 2
Don't know why, but this thing really got me. I watched this movie recently, so it might just be my clouded judgement, but I'd still recommend this to anyone in search for a bit of a thrill.
There are certainly more horror movies that got me scared, mostly asian ones, but it'd be a right pain to list all of them. So I'm going with these two. c: