Over on Blog O'Stuff, I have a few posts up here, here, and here about my latest acquisition, a Ruger 22/45 Lite. In my opinion, a .22 pistol is a very worthwhile addition to any prepper's toolbox, and Ruger's autoloaders are amongst the best available.
A .22 allows you to shoot a lot for little money, is good for new shooters due to the minimal recoil and noise, and where legal for hunting, is ideally suited for bagging small game.
Several years ago, I bought a Ruger 22/45 with a 4.5" barrel and fixed sights for my wife to learn how to shoot. It's proven to be very reliable, even with bulk pack ammo. The Lite's aluminum upper with a stainless steel barrel liner weighs only 22.8 ounces unloaded (without an optic), and most interestingly, is threaded 1/2x28 at the muzzle for a suppressor.