I've shot several military arms, AR-15s, AR-10, M14, CETME, HK91, SKS, AK-M, Arisaka, 1903A1, M1 Carbine, Mauser, Mosin etc.
If I had to pick one to survive, CETME or HK91 ( same basic design ) would be my first choice. Accurate, good sights, simpler than gas operation and in a common calibre...