This film had a genius marketing strategy. It showed the infamous shot of the Statue of Liberty's head getting thrown in the street, then only a release date. No title and nothing else about the plot. The film itself was very clever and lived up to the intriguing hype. (IMO anyways) Although I did get a little motion sickness when they were running up the stairs with the camera pointed down.
2) Home Movie
You kind of have to suspend your disbelief during an important part of this film, but other than that...it's creepy as hell.
3) Zero Day
This is one of the most interesting films about school massacres out there, and it feels so authentic. I know this isn't the typical horror film, but it's still prety frightening what these kids pull off.