as much as I hate to admit it, a few good .22s would be much more usefull than a shotgun or any other gun for that matter (well besides a minigun I suppose). the round is easy to place, fast shooting, low recoil, and you can carry a butt load. its high enough power to go through a rotting zombie's skull. if picking from big boy guns I'd have to say an AR and a high cap 9mm. lots of rounds because all you can really go for are head shots. the stopping power of the .45 doesn't matter in such a case, its all about getting through as many skulls as possible