I own a Remington 870 Express with an 18" slug barrel - 4+1 rounds of 12ga. juju. I got it at Wal-Mart for under $250 a couple of years ago. That's a WHOLE
lotta hurtin' for not much money!! Another plus for the pump action is its feed/eject reliability.
My "dream" shotgun is the Benelli M4 auto with magazine extension, tritium sights and pistol grip. I can't see how it could get any better than that for a home defense shotgun. I have fired a friend's Benelli, and the recoil is 1/2 that of my 870.
The Remington 870 will do a great job of HD; it has been the standard for decades. The Remington 1100 auto is also a great choice, with a short slug barrel. The Benelli, configured for tactical use (as above) wins hands down, though - at around $900 American.
The 12ga. is pretty much the last word in home defense - it is light years ahead of any handgun in terms of "stopping power." It's almost like shooting a bad guy with a cannon! And facing that 3/4" bore may be all that is needed for the BGs to start seeing things your way.