Interest topic. I've thought on this some and discussed it with others. My conclusions are that it comes down to whether you think you'll have more of a need for hunting game of different types for food, or whether you think you'll be fighting others off, defending yourself, or going on the offensive.
Also, if you live out in the country and think all you're going to need is a deer rifle, how long will it be until starving folks from the cities are in your neck of the woods?
My guess is that a blended approach of the most common calibers is probably best.
.38 spc, 9mm, .40, .45, .223/5.56, .308/7.62x51, 12g buck/ slugs, and 7.62x39 for defense/offense.
.22lr, .44mag, 30-30, 30-06, 12g everything, and maybe .270 and 7mm for hunting.
Even more fun is also having the tools on hand to use all of that ammo, in case you need it.
I doubt a lot of folks will be looking to trade some .356TSW or .257 Roberts ammo for a bag of rock salt.