Another gun that every gun collection simply needs to have is a shotgun. The reason why is purely because of practicality: shotguns are incredibly practical because of their ammunition. Birdshot can be used for bird hunting and small game hunting, buckshot can be used for home defense, and slugs can also be used for home defense as well as big game hunting within moderate distances.
One of the most successful and reputable shotguns ever made is the Mossberg 500, along with its variants the 590 and the 590A1. The 500 in particular can be equipped with both short and long barrels. The short barrels would be good for home defense, and the long barrels good for clay pigeon shooting and for hunting.