water, a portable water purifier (one of the ones that removes micro-organisms), camping dishes, a portable stove, freeze-dried ration packs/tinned food. Personal hygiene requirements, first-aid kit. If I could afford it, a porta-potty or else some other way of dealing with human waste (if you are in an urban environment with no functioning sanitation). Blankets, tent. (a proper, small camping tent, not one of those huge home-away-from-home ones).
Medications are important, but with the short shelf life, I'd just make sure you keep any prescriptions filled and together in a place where you can grab them quickly. If I was seriously concerned about natural disaster.
Also keep a portable file with essential personal documents, ID, passport, recent bank statement, mortgage, birth certificates, ready to grab. Ideally, photocopy them and send a copy to a relative to keep.
Work out how far you'd need to go in the event of whatever is worrying you, and how much gas you need to get there compared to the volume of your tank.
We live in the country, so I've lately been trying to make sure I keep at least half a tank - we aren't that far from town, but I can guarantee the day I need to make an emergency hospital dash is the day I'll be running on empty!