10mm. A very versatile cartridge with a good balance between magazine capacity and power, and bullet weights ranging from 135gr to 230gr. 10mm is my "does all" caliber.
No, I have a S&W Model 19 (the 357 and 38's) and a NAA 5 shot derringer with the swivel clip apparatus that has interchangeable cylinders (22lr and 22mag).
After your post, I might just be in the market for said Ruger convertible tho! I'm all about standardizing my ammo supply and the means of delivery.
I personally LOVE .22LR. Cause it's cheap to shoot and fun. I can shoot ALL day for about $20. And that generally buys quality ammo. Where as that same $20 buys me about 15 minutes with my Sig 9mm.