ALL GOOD
I agree with everything everybody said above. ANY shotgun makes a fine social gun to keep around the house.
I have a Winchester Defender 1300 12ga. I think it was around $400 new 6 or 7 years ago. I like it - 12 ga, high magazine capacity (8), short barrel (18"), all matte black (low maintenance). As for ammo, I use 00 Tactical Loads but, as mentioned above, anything will do - birdshot, trap loads, etc. I wouldn't want to be on the receiving end of any of them.
One thing to keep in mind is the rather short effective range - what? <20' or something like that for the knockdown you'd be looking for in that type situation, i. e. , one shot stop and throw 'em down backwards. Speaking of one shot stops brings to mind another thought: if you ever, God forbid, are in a situation like that always rack another load into the chamber as soon as you fire -you never know...
There is an excellent training video "Tactical Shotgun", made by Gunsite, a well respected training facility in AZ. The video discusses gun choices, aftermarket add-ons (bombing?) and tactics. I bought one (and a few others) through Dillon Precision (reloading machines and alot of other gun stuff), also in AZ. I think they both have websites for ordering. I also enjoy receiving Dillon's catalog every month - "The Blue Press". It's free and always includes a few good articles, not to mention the famous monthly Blue Press covergirls. BTW, Dillon is one of those rare companies that maintains excellent service/customer relations. I can find the 800# for Dillon if anybody needs it - let me know.
Get a 12 ga and practice with it - recoil isn't bad if you know what to expect.