When shotguns are dramatically pumped at every opportunity, even when there should be a round in the chamber. Three things: one, you just ejected a perfectly good round. Two, when you've got an unfired round in the chamber, you need to hit a special release button/lever to unlock the slide. Three, it should only ever be necessary when the magazine is empty, despite what supposedly realistic games/movies would have you believe.
It may not be obvious to the average person, but to me, it's like seeing someone get in a car, driving a block, and then turning on the engine.