The House of the Devil (2009) 
My nerves are TATTERED. Never have I been so frozen in fear as when a set of fingers close around the edge of a door... I saw a lot of people saying this is too slow, I think that they are wrong.
This film starts off like a day in the life of Sam, she goes to rent a new apartment because her room-mate is a nightmare, she has pizza with her best friend, she bags a job as a babysitter only where is the baby? Each turn of events brings the tension a notch higher until, Sam exploring the house to find the source of the creaking she can hear, pulls a light cord only to fuse all the lights in the house.
Panic sets in and reaches fever pitch when that set of fingers curls around the door. I'm right with Sam as she starts having a panic attack, everything going out of focus and she starts to pass out. What follows is freaky, and even with the Satanic Panic disclaimer at the beginning I didn't expect it, but it shifts the tone a little too much into fantasy which spoils the tense atmosphere of the previous 80 minutes.
It could have been 5 stars and I don't know how I would have made it different, but it was still a really good film and I highly recommend if you have the patience for a film that builds rather than screams!