A 4"-5.5" 657 or a 4" ruger redhawk .357 mag or .41 mag.
Or a 4 inch 610.
Or, in fantasy-land, a ruger vaquero bird's head sheriff in .357 mag to match my .45 colt model. (High gloss stainless.)
Or since we're in fantasy-land, a .357 r-max blackhawk.
Well, if we're talking new guns, I'd like a Glock 26 to play second fiddle to my G19.
However, if we're able to conjour up a used gun we've been hankering over for awhile, I'd like the S&W Model 45, that is, the .22 Long Rifle Military & Police, AKA the Post Office gun.