August Underground...
http://imdb.com/title/tt0412467/
I've seen 100's of horror movies, but this 'tops' it all.
It's a simulated snuff movie, filmed amateurish (on purpose)... It looks so realistic, it's extremely shocking and scary.
I read the second movie in this series is even more disturbing (
http://imdb.com/title/tt0410332/)
If you think you're tough because Saw or Hostel doesn't do anything to you, try and see if you can stand this one. (I'd not recommend it though, I turned it off after 20 minutes of watching)
This movie takes horror to a whole new level, which is just over the top.