I have read of a couple of writers who decided they would pick the .22LR as their one gun if forced to make that decision.
One was the Late Skeeter Skelton who picked the .22 rifle, while old Alaskan writer Russel Annabel chose the Colt Woodsman in .22LR.
Then again Sherif Wilson said he would pick the Ruger Super Blackhawk in .44 mag.
I personally would go with a 12 gauge automatic. But if I could have two, the second one would be .22 auto rifle but I would hate to have to leave out the Beretta model 70 in .22LR.