Most of this has been covered....
An air hose with a glad hand and a dual straight footed chuck to inflate low tires. The primary cause of blowouts is low pressure due to not checking often enough. You can keep inflating a leaking tire but a blowout usually parks you. I'm always surprised at the number of drivers that don't even bump the tires once a day.
I keep a bicycle inner tube and some hose clamps to patch a trailer airline, I have never used it, but I've seen ice covered air lines dragging on the road. For the winter I also have a cheap propane torch to warm frozen brakes, it's faster than beating them forever with a hammer.
Fuses and lights, electrical tape. Two pair of vice grips to clamp off air lines to a brake can. After using the key to back off the brake you can clamp the lines and rebuild pressure and drive again. Others have told me you can put a penny in the connection and tighten it down instead of the vice grips and DOT won't notice your "repair" as easily.
It's winter time so don't forget to check to make sure the fuel your using is winterized if you will be traveling into low temps. If you fuel in AZ and head up north you may need to add anti-gel.
An extra cam tool (don't remember what its called) for your tire chains. The cams can be a real pain to tighten without one and I leave on in the snow at least once a year.