Here's a couple examples
Nice idea for a thread. I went through my collection, and was able to find these good examples.
First, a 69 cal 1822 French Calvary percussion pistol with a Belgian liege 41 cal percussion derringer.
Next, in firearms development, we have a 1858 Remington 44 cal percussion revolver (a real one, no repros for me : P) with a Colt 1849 pocket model 31 cal percussion derringer.
Third is a 2nd gen Colt 45 Buntline with a Colt 22/22mag convertible New Frontier Buntline.
AMT hardballer Longslide (featured in Terminator) with a Bauer 25 auto (Baby Browning copy).
Fourth is a nickel S&W 29-2 44 mag with a nickel S&W 34-1 22/32 kitgun.
And finally, the biggest goliath, with the weakest David: S&W 460 XVR (Whitetails Unlimited - New York - 1 of 100) with a S&W 2nd model Ladysmith nickel 22 long (not LR). The X frame (biggest) and the M frame (smallest).