You use whatever you have available.
Believe it or not, there are alot of gun owners out there who are not gun nuts. They may have an old single barrel Harrington-Richardson break open from gandad, or maybe its for shooting pests in the garden plot out back. They don't go to the range, don't even own a handgun.
But when the big bad wold is pounding on thier door, and their scared, they will grab whatever is there. It may work as most burglers don't want to get in a gun battle.
A while back I saw in the Armed Citizen in the American Rifleman and old guy and his wife were tied up and left in the bedroom while a group of burglers ransacked thier house. Old guy got loose and retieved a .22 bolt action rifle from the closet and chased off the burglers. The rifle wasn't even loaded. Brave bunch.