Mercifully, the challenge here is to pick one's one and ony REVOLVER, not one's one and only handgun. Given that limited challenge, I'll take my custom Ruger Bisley 44 Magnum with 4-5/8 barrel. This gun can handle all my steel plate and long range shooting, plinking, hunting. I'd leave the CCW concerns to my Browning Hi Power and other semi-autos.
Where the challenge to pick a revolver that would be my only handgun, my M19-3 2.5-inch would be my pick. I have made a committment to be separated from that gun only when absolutely necessary, and at the end of the day personal protection is my first priority where handguns are concerned.