I agree with Larry. Chambered in all kinds of guns. Fun and easy to shoot. Accurate enough to get all sorts of jobs done. Ammo is cheap, easy to find and doesn't take up space. We all know what carrying 50 rounds of .38 special feels like, or 20 rounds of 30-06. A 50 rd box of .22 fits easily in a shirt pocket. I can teach my grand daughter to shoot a .22 and she'd have fun. Can't say the same for most center fire cartridges. I'm not saying that the .22 is perfect for any situation but, if push came to shove, or if I could take only one gun with me, in most situations I could make do with a 22.
John