In all practicality a 3" chambered 870 with 26" VR Remchoke barrel is a true workhorse. I can't think of anything more dependable and widely used; parts and repairs are simple.
A sturdy German double with a little extra underneath is my idea of the all-around shotgun...a Merkel/Simson/Fortuna, they're all the same gun and are tough as nails.