I would go with a Pump-Action 12GA. Remington 870's and Mossberg 500's are one of the more common choices for people. I have both, I dislike the Mossberg for 2 reasons, the forend rattles like two skeletons having sex in a metal trashcan and the receiver is aluminum (Lots-O-Dings), but I love the tang safety on the mossberg. My Remington 870 has tighter tolerances regarding the forend, and I don't mind the crossbolt safety. Also, keep in mind that your shotgun doesn't "need" to be tacticool. I have the regular ol' bead sight, and carry 3" OO buckshot, 2 3/4 shells are "recommended" for HD in apartments or houses are closer together, but the choice is obviously yours. If it doesn't make you more proficient then don' get it (mag extension, side saddle,
flashlight/ laser, shell bandoleers, sling and anything of that nature) slings get caught in the dark, under stress you will probably fumble with a flashlight/ laser, too many extra rounds will weigh you down. Just keep it simple. Also, grab a few different loads: buckshot, #4, Low recoil and rounds made for HD, and run them through your shotgun to get a feel for whats comfortable for you.
Good luck.