I prefer high-quality, single-stack semi autos that weigh less than 30 ounces. They are easy to conceal, and that fulfills the first requirement for winning a gunfight-bring a gun. I am almost as happy with a S&W revolver, and I prefer the j-frame for concealment use, especially my 3" M60. A short list of semi-autos would include:
Sig P239, S&W 3913 (or 908S if money is tight), Glock 36, Kahr K9/K40, and some of the light-weight versions of the 1911 from makers like Kimber or Springfield. I also liked the Para-Ordnance pistols that I had a chance to fire, and a C7 45 LDA is on my wish-list, even though it's a little over my usual weight limit for trouble-free carry. I guess that's not such a short list, but you wouldn't go too far wrong with any of those pistols, chambered in 9mm Luger, 40 S&W, or 45 ACP.
For a super-tiny, last-ditch backup, consider the NAA mini-revolver in 22 WMR, or the Kel-Tec P32. I'd rather have one of the other guns that I've suggested in a gunfight, but the NAA and the Kel-Tec can go anywhere with you, very discretely. They are purely short-range guns though, at least the ones that I own. That could be operator error, however, as they are not easy guns to shoot well. :wink: