Creep

This movie was horrifically tense.  I loved the pacing of the whole movie, and it was one of the few movies to give me a genuine sense of unease the entire time.

I don't want to spoil anything, so I'll hit minimal points.

The whole thing is shot in the found footage format.  Usually, I don't like that, but this one really worked well.

Secondly, you never know throughout the movie exactly how it'll end.  That made it really great in my opinion.

The only bad part is that it relied a little heavily on jumpscares for it's scare moments.