EAS!!!! Driving from CA to TN

A 2gallon gas can and an extra ballast resistor if you run one are nice things to have with you.
6' of primary wire, a test light, spark plug wrench, 3/8, 7/16, 1/2, 9/16 and 5/8 wrenches.
One each flat and Phillips, needle nose pliers, electrical tape, and an extra gallon of water.

I consider these tools to be a minimum must have on a long trip outside of the obvious stuff like a good spare tire and a jack, drinking water, and a first aid kit with a needle and thread. :D
Firearm protection is an absolute must as far as I am concerned, and especially with all the little side trips into tweaker towns you'll be making.