Lots of good suggestions here but the most important ones IMO.
Duct Tape.
Pocket knife.
1st. aid Kit.
Blanket.
Snacks.
Flash light.
Water, lots of it.
And keep your gas tank full. In the west you will often
see signs that will say " Next gas 75 Mi." It's true and even
then when you get to the station it might not be open or the owner
might have gone fishing.
Most often you will find these signs 15mi. on the way out of town.