Back in July we told you about Army Ranger Sgt. 1st Class Leroy Petry, who was the second living American to be presented with the Medal of Honor based on his service in the war in Afghanistan. (Our old pal Sal Giunta was the other.) During an operation in 2008, Petry and his fellow Rangers came under fire by insurgents, and after getting shot in both legs, he saw a grenade thrown at him and two of his buddies. He picked up the grenade and tried to throw it back; the move sort of worked: he saved their lives, but his hand was blown off. Brandon's original post on Petry included the official description of the Ranger's heroic actions and a video of the Medal of Honor ceremony with President Obama. But last night, Petry was a guest on the "Late Show with David Letterman" and his version of the events is riveting. Also very cool: his new prosthetic hand, which is a marvel of modern science — and can pop off in an instant to show what it looked like in the moments after he lost his hand. This video is a must-watch.