Are you going for practicality or cool factor? If I had to choose I'd go with the Mini G. Although some people might call it blasphemy to modify a Garand.
There are zombies? What the hell are you going to do? Grab an M1 or M1A and a couple hundred rounds of 30-06 or .308 and save the world? Face it man, you're ****ed. Even if YOU do survive all the women that survive without won't be Angelina Jolies in a PVC body suit and matching HKs. They'll be...
I think g shocks and other high end watches have magnetic sheilding. Which is useful only if your an electrical engineer or an mri tech. Other than that i think minute precise time keeping would be the least of your worries, in a shtf i think a stick in the dirt or using your hands to gauge how...