I know of one which was blatant second degree murder, but the perp was a "friend" visiting with a few others to the victim's home, all around 14 years old. Taking a gun on its way to the safe you found in a part of the house no one was supposed to be in, pointing it at your "friend's" head and pulling the trigger was ruled an unfortunate "accident."

See a bunch that just so happened to occur while the gun was "being cleaned," you can even begin that without emptying the chamber so you can work on the barrel.