Sure, they are an extremely cool pickup for novelty’s sake when you are playing an FPS videogame. However, you cannot have one in real- life. In fact, not even the military, for whom they were designed, really uses them. That is because they are really better suited to knocking down drywall or demolishing concrete than they are to being a combat or hunting weapon. This is for several reasons:

1. They can only use high-powered ammunition, because the kinetic energy dispersed by less powerful shells cannot drive the automatic mechanism and cycle the action of the gun. In addition, to take full advantage of the automatic feature these guns are most often equipped with box or drum-style magazines and are unwieldy and heavy to aim.
2. They are very inaccurate, and rely mainly on coverage and fire rate to score hits on a target, mostly at close range. The short barrel and high power of the automatic shotgun maximize shot spray and ensure you will devastate anything relatively close to you and easy to hit, like a battalion of unarmed soldiers or zombies, or the broadside of a barn. For anything else you will hit it with some of the spray if you are lucky.
3. They contain many moving parts and mechanisms, making them a poor field gun and susceptible to jamming and malfunction. That rules out their usefulness in a majority of military contexts, and what other use do they have?

So, though the mere mention of the concept that is the automatic shotgun intimidates, that is about all it is good for outside of work more easily (and safely) done by a jackhammer. But you cannot own one.