Since unexpected shit happens, I already keep a few things in my backpack in case of need:
Mini screwdriver with multiple bits, lighter, strike-anywhere matches, sharpies, deck of cards, tiny medkit with bandages and disinfectant, bottle with 2 types of painkillers, pepto bismol, and some of my ADD meds in case I forget, and my swiss army knife with various container-opening tools.
What Cata has taught me: Have a backup plan in case you’re without home, and know how to at least field-dress animals.
A hatchet is a damn good idea for an emergency. I now own one, with a notch for nail-pulling and a flat end to double as a hammer. Plan is to look into a small tent kit I can fold away into my (kinda big) backpack, and get something for water purification on the go. While I don’t expect any zombie apocalypse, my city’s on a relatively minor faultline. It doesn’t produce earthquakes much bigger than 6 on the Richter scale, but none of the buildings here are designed to resist quakes.