I'm watching a movie called Rec at the moment, its a spanish horror film along the lines of the Blair Witch Project, Diary of the Dead and Cloverfield - the whole camcorder point of view thing. Unlike the others though, this one feels very distinctly and frighteningly real, from the incredibly natural performances given by the supporting actors (not to mention the lead actress) to the authentic sound effects and unprocessed audio during the louder scenes. One or two pieces break the sense of immersion like the video actually rewinding when one of the characters tries to watch a recorded sequence from earlier. Overall though, an excellent film and well worth watching.
It leaves me wondering whether the "authenticity" of the performances are because of fantastic acting or if my lack of familiarity with spanish leaves me unable to distinguish flat spanish acting from a hole in the ground.