I know I'm quite late here, and the decision has probably been made already. For my two cent's worth, I 'd say it was hard to beat the G26 9mm if you consider stopping power, concealability, simplicity, and accuracy. I'm not sure how cost would compare with other similar options. The G26 is not my favorite gun, but for a woman in particular, it offers the small size for both grip and concealment, it is amazingly simple to shoot or clean, has acceptable recoil, is accurate enough at self-defense distances, can be fitted with laser sights, is relatively cheap to shoot, reliable, and still has a decent stopping power. I have one, and carry it when concealabilty is most important. Still, my Kimber 45 is probably my favorite even though it doesn't conceal quite as well. Then again, if you just want to scare someone off, the S&W 500 is hard to beat. There's not much chance of concealing it, unless you're wearing a tent!