A 22 or 32 caliber Ruger LCR. Handguns are for carrying so I'll pick the one I can carry all the time and everywhere. All other firearm uses can be covered by long guns, however much of a buzzkill that would be.
Or pull a Malamute - pick a belt revolver and keep my mouth shut about the pocket snub. Probably a 4" pencil barreled S&W model 10.
Edit for the semi-auto subforum:
Belt: Beretta 92 FS/G/D/doesn't matter, PX4 compact in 9mm or .40, USP in forty, USP compact in forty, or G27.
Pocket: I don't trust any enough to live with forever as a one and only (particularly as round counts rise), go back to revolver selection.