All you guys who picked a .223/5.56 rifle are crazy.
Maybe in the US it would make sense, but here in Kanada we ocassionally have to shoot deer larger than 75lbs (the last one I shot dressed 220).
We have large predators like grizzly and black bears (yes they do eat people in my PERSONAL experience).
2 legged preditors wear various types of "body armour" from heavy leather & denim to ceramic plates for @8 months/year.
Y'all seem to be assuming a perminant July SHTF senario.
My take on a "battery" would include a 10/22, and a .22 REVOLVER,
1+ large caliber revolver (.357, .44, .45 Colt),
12 Gauge pump shotgun
.30 Cal rifle (.308, .30-06, .303 ect) & a .30 cal carbine (7.62x39 or .30-30)
You may note that I didn't include a semi-auto pistol? I'm even cautious about semi rifles?
Magazine based weapons are quite vulnerable to magazine wear and spring weakness. Unless you're planning a "summer vacation" senario, it's something to keep in mind.
To answer the original question: an M-14 variation for S/A and a (reasonably lightweight) Mauser, Remchester/Savage or Lee Enfield B/A to deal with any realistic SHTF senario.
While it would be nice to be able to pot the occasional coyote with a varmit cal, I think I'd need a more flexible cartridge over there in the "real world".