.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.
Mauser Werke, Schmidt-Rubin, Colt, Walther, HK, Weatherby, Browning, Ruger, Beretta, Savage, Bushmaster, Marlin, Mossberg, Saiga, S&W, Sig Sauer....a few friends of mine