I have a military and electronics background. I think the thing people will be able to come to me for is anything power-related. I can MacGuyver together generators (gas-powered and human-powered), inverters, solar power arrays, etc. I will be able to charge batteries for flashlights and radios, as well as wire up workshops or makeshift “homes”. This skill has practical/lifesaving value, as well as comfort value.
Maybe I could get you some power to run your medical equipment, or even charge up an electric shaver so you can groom yourself and your friends. Communication equipment will be a must, and cobbling together some surveillance gear, with a few cameras and monitors, and maybe even an alarm system, would be great too.
On an unrelated note, I can set up some mean and nasty booby traps.
Other than that, I can shoot, but why go out and do that when I can be tucked “safely”, in a workshop building things people need?