I've been camping and exploring since I was a youngster and I'm now 68 (behind my eyes, I'm still 35!). I was a California deputy sheriff for a few years but was never in the military. OK, that's my background. I have felt for decades that the best all around weapon for survival, practice, fun, economics, and suitability for the widest variety of situations is the .22 rifle paired with a .22 pistol. I have owned a Ruger 10/22 of one sort or another since I was 17 back in 1968.
It's not the most effective self-defense round nor the most effective round for larger game but between the cost, weight, accuracy, and ability to carry a thousand rounds or more easily, I'm hard pressed to accept that my AR/AKs or my larger bore handguns are a better *all-around* choice for a survival weapon. Sure, I carry my FNP-45 (15x.45 rounds) in my rig and either a Kahr PM9 or Ruger LCP in my pocket but if I could only own one firearm for all around use, it would be a Ruger 10/22 variant like this Magpul Backpacker stocked .22. Shotguns? Absolutely have one but it's not the best *all-around* weapon IMO. A guy with a .22 rifle, a .22 pistol, and a 12 gauge shotgun should be prepared for about anything.
I should add that there was a period I that the AR 5.56 was the best choice but these days, I think of that one more as a zombie apocalypse choice.