Sorry, but here is the honest answer: There is no one "ideal" survival rifle. You need to shoot small game and large game, at close range and far range, plus have an adequate self-defense round at medium range, and there is NO single cartridge that fills that bill nicely or even reasonably close. Sorry, but it ends up being a series of very bad compromises. Perhaps the closest bad-fit is a .223 rifle, with a chamber insert for firing .22 LR.
The next closest bad-fit would be an M-1 Carbine, with a 3 power scope mounted, using fmj rounds for small game, and soft points for large game and zombies. This would give you close-up capacity on small game, a reasonable big game round to 100 yards, and a reasonable self-defense round to 150 yards. (The .30 carbine in the soft-point version is a totally different animal than the fmj round, and yes it would be devastating on a zombie at 150 yards, delivering about the same foot pounds of energy as a .357 magnum fired at point blank in a revolver.)
The best fit for all situations would be to have two rifles: one in .22lr, and one in either .308 Winchester, .30-30 Winchester, or 7.62 Russian. This combo would totally fill the bill up close, and out to 200 yards. (Yes, the .30-30 is a 200 yard round. Just sight it in 6 inches high at 100 yards.)
Now, someone may say that you can get one of the Savage combo guns, with the .30-30 barrel on bottom, and the .22 LR on top, but sorry, that won't do it. You definitely need a repeater in the larger caliber, and you definitely need the ability to mount a 3 power scope for the larger caliber.
So, get a lightweight .30 caliber rifle, with a 20 inch barrel, and get an ultra-light .22 LR with an 16 or 18 inch barrel, that will break down into a small carry pack, such as the Marlin Papoose, or a Henry Survival Rifle, etc (that stores the barrel inside of a plastic stock).
Regards,
Mannyrock