127 Hours - this is the true story of a hiker that got his arm stuck under a rock for 127 hours and ended up cutting off his arm with a dull knife in order to survive. They show every little detail. Him breaking his arm, cutting through muscles, ligaments, veins, etc. Abso-f-ing-lutely disqusting and painful to watch, but you couldn't NOT watch.
It was a very good movie and the best thing James Franco has ever done. (Which I know is not saying much, but he was really great.)