Crap...I don't think I have 200 million rounds of .223!
Hk93A3, AR15 (M4 style as backup in same caliber because I'm not hauling a Benelli and 12ga shells as well all over hell's half acre), and Glock 21 or 30. It would take a while to decide. I really doubt a conventional war of that scale would occur though...
Oh, wait...you said FINAL battle...in that case some holy water, a cross, and a cool pope hat! Safe passage for judgement day.