Power nail guns are quite dangerous, and even though they have a pretty good safety trigger, they are not accident-proof. One of the many ways you can get shot with a nail gun is for the gun to be too close to the edge of the board that is triggering it and for the nail to miss the board completely.
Over the holidays, someone that I personally know (whom I’m not going to identify, because they’re embarrassed enough as it is) accidentally shot a 10d nail into their arm near the wrist. The nail hit the bone and it actually bent the nail a little bit. Thankfully, the bone was not chipped or hurt in any way and this person made a quick recovery with only a slight bruising of their pride.