Glock model 21 in 45 ACP.Slow round but a bunch of lead.If your really into handguns or any gun for that matter,check out the taylor energy calculator.Retained energy is some serious stuff. http://handloads.com/calc/quick.asp
Oh I just tuck it in my waist band.I will be curious as to which weapon you choose.9's have very cheap ammo and high cap mags,something to consider.They have a speed higher than a 380.Same bullet.All guns will defend you,used properly.
I like the 9mm, although I never shot anyone with one I shot some dogs and stuff like that in Iraq with the 9mm ball ammo which is about useless, with a good hollow point it is a good round, at least better than a 380 or 25acp. I also agree that anything will work when used properly.
on the civilian side, I have seen about every caliber of GSW you can think of and its all shot placement.
for the nay-sayers when they get on the 9mm round i ask if I can shoot them in the leg with mine. since its so puny it wont hurt, I have yet to have a taker on the offer.
SIG P239 in .40, carried via a Galco OWB holster. Unless I'm wearing something form fitting the OWB holster works fine. I keep it loaded with hydrashocks and always carry my little surefire light with it as well.
I'm considering switching over to an M&P 40 for every day carry, as its the pistol I've put the most rounds through and have the most experience with. Its slightly larger than the 239, but I'm sure I could find a holster to make it fairly well concealed.
Something of the 1911 design, in 45 Auto. A 9mm will give you more shots, but in a self defense situation, you are not likely to need 17 shots. The 45 is not a light weapon to carry, but to quote Col Jeff Cooper, "A gun should be comforting more than comfortable."
Springfield XD Sub-Compact in .40 S&W. Plenty enough rounds for a prolonged engaement (which you hopefully woulnd't be in in the first place) and plenty of power in a small, controlable package. 1911 style ergonomics and every bit as reliable as a "block". As for the Serpa holster...I see alot of negative reviews. For a smaller auto, there is no reason not to have a nice high-ride tight fitting (to your belt) Fitted polymer paddle holster. a quick brush up of the shirt and down with the web of your on hand and it's right there for a quick, easy draw should you need it.