Which firearm is designed to fire slugs and may have rifled barrels?

The correct answer is a shotgun, as it is specifically designed to fire both balls (known as slugs) and shot, and may come equipped with rifled barrels. A shotgun's rifled barrel allows it to stabilize the slug, providing greater accuracy over longer distances compared to smoothbore barrels. This versatility makes shotguns suitable for various hunting situations, whether for small game with shot or larger game using slugs.

In contrast, other firearms listed, such as cannons, rifles, and pistols, have distinct designs and operational purposes. Cannons are large artillery pieces that fire explosive projectiles and are not typically used for hunting. While rifles are designed for accuracy and can also be used to fire slugs, they are generally not classified as shotguns. Pistols are hand-held firearms primarily designed for personal defense and target shooting, lacking the capacity to fire shotgun shells. Therefore, a shotgun is the distinct firearm that meets the criteria outlined in the question.