I have a pretty complete metric and standard socket set, screw drivers, a set of Torx bits, tire pressure gauge, 4-way lug wrench, wire cutters, spare fuses (duh!) and washer fluid.
Oh, and perhaps the most essential tool of all is a good quality headlamp. I have a Petzl 4 LED one. They're compact and long-lasting. All of the tools in the world are great, but if you can't see what you're doing, then there's no point in carrying tools at all.
My $.02
