There is no doubt about it that the shotgun one of the most versatile single shot weapon in existence. This is due to the design of the ammunition it fires, which are essentially shells with ammunition inside along with the gunpowder and primer part. It is the existence of the shell that makes it so versatile.
The shell enables anything that fits into the shell to be able to be fired out the shotgun. Because of this, you have the bird shot, the slug, and the buckshot. The different types of ammo allows the shotgun to be used for hunting animals of all sizes, including humans. Other than the traditional ammunition, hobbyists have dedicated themselves to creating all kinds of strange unconventional shotgun ammunition, and some of the stuff they have made are quite scary.