This dude got his thumb snared in his equipment, fell, and sliced it off. The thumb, sans climber, landed on a ledge by his partner, who picked it up and brought it with. Surgeons reattached it later at the hospital.
Insane rescue on Half Dome in Yosemite 09/26/2011
Clickthrough not for faint hearted.
*el cap, not half dome.