A good multitool.

A good umbrella, golf size if possible. Keeps the rain and the sun off you. Damn useful if you find you have to walk a ways or wait by the car.

Two Maglite flashlights. One AA model in the glove box and a bigger three D cell one in the trunk. Oh, extra batteries if possible.

Some tools - multi-screwdriver, a 3/8 and 1/4 ratchet set, if possible, and a pair of Vise Grips pliers.