I'm pretty tired of zombie-themed things, but I have to set the record straight here. G&A lists the common handgun and rifle calibers, to include .308win, .223/5.56x45, 30-30, .270, 9x19mm, 45ACP, 44 Rem Mag, and .38Spl. Wrong, wrong, wrong, wrong, wrong, wrong, wrong, wrong, and wrong. Those of you who are also gun nuts, go get 100 rounds of any of G&A's calibers listed, then get 100 rounds of .22LR and tell me which one you'd be more mobile with.
Additionally, you can get wildly accurate and anvil-reliable .22LR semi-auto rifles, chief of which is the venerable Ruger 10/22. You can also get equally reliable and accurate .22LR pistols like the Ruger MKII/III and Browning Buckmark. Conversions for 1911s and Glocks are also available.
In every zombie movie, there is a horde that must be escaped or a building that must be defended. Well, in either case, each person in your surviving band could carry two or three thousand rounds of ammo. Additionally, the .22LR is so low pressure that guns chambered for it have a virtually unlimited service life with only the most basic maintenance. The old .22LR doesn't burn up barrels either, though leading can be a problem with softer projectiles. But that can be cured with a quick brush and rod or bore snake if time isn't available for a proper cleaning.
To my mind, the .22LR is a great solution for a number of real-world problems, as well as whatever imaginary ones we can come up with. But Hornady probably doesn't make Z-Max ammo in .22LR.