Best All-around Gun an AR-7
No question - an AR-7 in .22 LR. Very light weight, so easy to pack and carry, short for storage, floats, very accurate and reliable (Yeah, I know not everyone shares this opinion, but I have two of them and both of mine actually are), mild report, and lethal (while I haven't done it, my daddy killed quite a few deer with a .22 LR using head shots). Plus you can tote a lot more .22 LR rounds than anything bigger, and .22 LR ammo is much more likely to be available anywhere on the planet than any other caliber. If only there was an AR-7 in .22 Magnum, I'd probably go with it. If I could have ONLY one gun in an EOTWAWKI situation, it would have to be an AR-7. Second choice would be almost any 12 gauge shotgun. I wouldn't worry much about concealability. If I could have a handgun in addition, it would be a Ruger .22 automatic, for commonality of ammunition and reliability.