.22 LR can easily kill small game or medium sized 2 legged game if req'd for defense. It was cheap and plentiful and still is relative to the prime calibers, and can be used in untold different firearms. So yes, it's good to have a big stack of .22 LR!!
I've never seen .22 LR sell for such absurd prices as lately. Glad I already have everything I need.
My advice is also to have a few good effective oddball calibers, many of which can still be found at regular prices and in normal quantities. If you relied only on 9mm for example and didn't have much, you'd be screwed.
1944 Mauser byf K98 8mm, K31 7.5 x 55 Swiss, Rem M700 Classic 8mm, 1920s Colt New Service .45 LC, Browning Hi-Power and HK P7 in 9mm, SAIGA .308 22", SKS 7.62x39mm, S&W 686 Plus 6" and Taurus 617 2" in .357 Mag, Ruger MkIII Target 5.5" BB .22LR, Mossberg 500 & Marlin 120 in 12 GA, etc.