This is one I've been debating. I wanna say my Kriss Vector with my G21. Really, if the S hit the fan I think an AK47 and a 1911 will never fail you. Plus I build AK's so for maintenance it would make since.
If it were just me trying to survive in the wilderness, I would prefer my scoped Ruger 10/22 carbine and a Polymer frame Sig 9mm. If I were in a combat situation, I would want an AR and a 1911 in .45 ACP.
If I was having to hunt for food while defending myself from aggressors, then I would want three weapons, AR, 10/22 and a good pistol.