I read about this guy years ago, and it was quite sickening to hear the full gory details. Aron Ralston got his arm stuck under a rock in 2003 whilst out climbing on his own. He had not informed anyone where he was and had no cell phone. After 5 days with little food and water, he realised that if he wanted to get out, he would have to cut off his arm. He used a cheap multi tool to cut off his arm and was then eventually rescued.
Just reading about the ordeal was bad enough, but at the screening for the movie, 3 people fainted!