Either a Springfield 1903, or a customized M70 with a stainless barrel, in .30-06. Most common round near where I live, the customized M70 would work for hunting and long range duty, the 1903 would work for the same and be more robust.
For a handgun, most certainly a .357. If you find .357 ammo, use it. If you find .38 ammo, use it. The best option for this would be that Medusa revolver from not too many years ago, that could use .380, 9x18, 9x19, .38 special, and .357 mag ammo.
If I had to have a semi-auto, I'd probably take a 1911. There's plenty of them out there, .45ACP=.45ACP, many parts are interchangeable (if I find one elsewhere, keep it for spare parts, etc). I would like to carry around something different, but in the off chance that this is supposed to be the "end of the world", and I am intending to have this thing the rest of my life--well, a crapload of Americans have 1911s, and if I'm using one with GI parts, I can pirate those out of other people's firearms, because no matter how many customization options one firearm may have that another doesn't--chances are, stuff'll swap. That's not guaranteed on most other platforms/calibers of weapon.