I’ve read that those who live in Grizzly country would choose the Winchester Model 71 in .348win if they could only carry one weapon. Unfortunately since these became collector items the ammunition is no longer manufactured by Winchester.
I live in bear country. The most common walk in the woods bear guns I see are .45-70 lever action carbines or 12 gage pump guns. Major caliber rifles for subsistence and sport hunting - moose, deer, bear, sheep. .22 LR for small game. Bear protection is another matter. Shots are always at very short range and there will almost never be time for a second shot.
My “One gun” is a Mossberg 500 Mariner 12 gage; Bird shot, buck shot, bear slugs. I won’t be doing any sporty long shots in a SHTF situation nor will I be engaging in any protracted firefights. I will be doing everything possible to get away from other people. I will need to feed myself and my family and protect us from predators while traveling as far and as fast as possible, probably on foot. For me there is no danger from marauding urban ferals. The danger is from having food supplies cut off or running into a mama grizz on short notice.