Bankroll is the only limiting factor, there's just so many options to choose from. If money is no object, something like an FN Police special sure would be nice. Remington 870 seems to be a real reliable choice. Mossbergs are inexpensive, and get mixed reviews. There must be some threads on that. I would guess for HD, a shorter barrel would be best. 18" or so. I prefer a pump action, simply because there is less to go wrong. As for loads, I don't want to start a broo-ha ha, but some of the tests by boxoftruth and others have furnished some surprising results in regards to how much 00 buck can penetrate walls and such. Really anything will, but the 12 gauge loads are scooting along pretty good. I would avoid magnum loads. They compromise your capacity anyway. From what I have read, something as small as #1 or smaller is adequate for close range and lessens the likelihood of overpenetration. Thing is, I have searched high and low and can't seem to find anything 1-3. 0 or #4 is all I seem to run across. Whatever you decide on, I would make sure it performs adequately in your firearm before settling on it. Not trying to talk down to you, but in addition to a decent HD weapon, I would make sure my house was secure, and have an early warning system (i.e. dog) in place, to let you know if someone is creeping around. Best of luck to you. Be safe.