Wouldn't ya know...
I volunteered to help my brother-in-law frame out his soon-to-be-renovated/enlarged upstairs bathroom after I learned he'd injured his hand when his right hand made contact with a circular saw he was using to enlarge his roof opening (he's adding a dormer) after the ladder he was standing on moved suddenly. Fortunately, he's okay. He'll have the scars and maybe some loss of motion/feeling, but all five digits are still there.
After working the past five weekend days in the heat stripping shingles, working out compound angles and cutting sheets of plywood, it happened. I was trying to attach the last stud of a soffit frame to the ridge beam and, after climbing up into the rafters (about 20' up in the air), decided it would be just a little too much trouble to move into the correct position to shot the framing nail (the stud had a slight twist and was off position by ~1/2"). Needless to say, I was tired, hot and impatient to finish. So I reached up with both hands, aiming the gun at the stud (and facing slightly back at myself...you can see where this is going, can't you?), pushed the stud into position and pulled the trigger.
Sure enough, the action of the air piston caused the tip of the nail gun to shift slightly and before I could blink an eye, the nail gun fired a brand new 16d framing nail about 1" into my left forearm. Oddly, it didn't hurt much. I looked down, realized what a stupid f'n decision I'd just made and pulled the nail out. I then moved into the correct position (due to a sudden shot of motivation), shot the nail using the right technique the second time and climbed down.
Fortunately for me, the nail missed my artery and any/all bones and bled only a small amount on removal. I had my niece bandage me up and asked me wife call my doctor. He indicated I didn't need to visit the clinic for a tetanus shot as I'd had one in the last 10 years. A day later and there's no real pain, no swelling, no nasty black & blue mark. I consider myself a very lucky man. So, for all those who work with power tools of any kind....take your time and be careful, the life/limb you save may be your own.