I live in a large urban area so these would be mine:

1.) Terror attacks
2.) Black-Outs
3.) Earthquakes: not likely but you never know
4.) Blizzards

I've lived through most of these and have gotten by with these absolute basics:

1.) Pair of sneakers/comfort shoes: In urban (NYC) shtf scenarios you must absolutely walk home. No busses, no trains, and no cars (street light power failures will have you sitting in your car for hours and hours)- cars jammed for miles.

2.) Flashlight: If you walk home in a black out or after-dark terror scenario, street light will not be working. A flashlight is indespensible. Flashlight and LED micro light too.

3.) Portable Radio: This is of MAJOR importance. We live in the days of iPods, which have no radio. A radio will allow you to hear what's going on if you are in the middle of the street and can't get on the subway or into your place of business. Radio, radio, radio.

4.) Charged cell phone