Well if you are having second thoughts about shooting someone why even make the thread?
I'd buy a good name brand, not some Chinese made Hi-Point that all the dumbfuck thugs use. I plan on buying a Glock 17 for home defense. Dead nuts reliable and they are chambered in 9mm so ammo will always be around. I wouldn't use anything less than 9mm for home defense, I know a lot of other people will feel differently but that is all preference. Another good one is a Walther PPX, I bought it to carry, but they make excellent nightstand guns as well. 500+ rounds of different manufacturers ammo through it and not a single hiccup. New they are like $500? Used I got mine with maybe 2 magazines through it for $400 OTD.
Whatever you do just don't cheap out on some Chinese junk that shoots .22. If you do, you might as well stick to using the BB gun.