Unfortunately, my collection of firearms is somewhat limited. I only own three autos, two of which are .22LR's. So, that leaves me with my 4.5" XDm 9mm with the one I'd keep. Now, if I had my choice of autos as my only one, I'd pick something entirely different. Probably a full-sized custom 1911.
Same issue with revolvers, fairly limited in my collection.... okay, only one. My 6" Ruger GP100. I love it, but if I had to keep only one revolver of my choosing, it'd probably be a 3" or 4" .357. Maybe an SP101, GP100, or S&W 686 or Colt Python. (Hah! Python... don't see myself owning one of those anytime soon. Anyone wanna donate some cash toward my "MrSpiffy needs a Colt Python" fund??)