On the set of Zombie Cult Massacre, I saw a guy who had been shot by a 12-gauge shotgun blank. Do not shoot yourself with a blank. Do not shoot other people with blanks (unless you'd like to hurt them). Cecil Adams explains this here but leaves out the shotgun angle. Not that either option would be nice, but I'd rather be shot by a .44 magnum than a 12-gauge (at least at close range).
In high school, I knew an idiot who liked to shoot people in the chest with blanks from a .22. Even wearing a thick shirt and from across a wide room, it was like being snapped by a wet towel against bare skin.