This thread has pitted physics arguments and Mythbusters against a case report in a respected medical journal, Annals of Thoracic Surgery. In the case reported, a falling bullet caused enough damage that only the efforts of a very well-equipped and -staffed hospital saved his life, with means that can aptly be termed heroic: they opened his chest, stuck their fingers in the holes in his heart, worked for 15 minutes to get the heart restarted, put him on heart/lung bypass, then patched the heart and went on to the abdomen where the bullet still had enough force, after descending through the thoracic cavity, to lacerate the stomach and damage the spleen badly enough to make its removal the most prudent course.
The journal article went on, as medical papers do, to discuss similar cases that have been discussed in other journal articles.
Sorry guys, MythBusters and high school physics classes don't cut it. You argued that what actually happened couldn't happen. Extremely dangerous injuries that could easily have been fatal were documented by skilled physicians.
I am only thankful that no one defended the practice of firing into the air as a means of celebration.