Thanks for all the replies, some good advice here. I am leaning towards a pistol right now. I used to have a Ruger 9mm but sold it years ago. I've shot my friend's HK USP which I liked a lot, although they are pricey. If I was in a large house, I would stick with the shotgun, but in my apartment, the longest shot might be like 10 - 12 FEET, so a pistol might be better here.