.357
I only need to reload one caliber and can have ammo that will work in my 15oz 5 shot pocket revolver, 25oz 5 shot belt revolver, 4" 6 shot woods revolver, and 18.5" levergun (out of which it will match 30-30 energy levels and get into the low end of .35 Remington). I can do 148gr wadcutter loads that use a miserly 3 grains or so of powder, or 200gr bullets with 13 grains of powder. The .44 is versatile too but requires twice as much lead and powder. The .357 does it all well and really economizes on lead and powder. It's become my absolutely favorite round.