I was just thinking about this the other day.
For me: A good emergency kit in the car, that includes stuff for both humans and vehicles. Ideally it will be updated each season (probably need more junk in the winter like heat sources).
Tiny flashlight on keychain, a good one, like a tiny Streamlight or Photon.
Small multitool and/or pocket knife, ideally one that fits in your change pocket. Even if you dont think you need it, you'd be amazed at how often you use one when you do have it.
Toaster oven. Has frequently replaced my microwave and range.
Netbook with microsoft streets & trips and a USB GPS unit. Costs about as much as a good GPS navigator but is considerably more useful. Also need a car charger to be really good. As offline navigation on cell phones improves this is become irrelevant. But I still like my netbook.
Even better is an Aux jack on my audio system and a dub cable between it and the computer.
Big box of gum, much better than buying a pack at a time. Keep it in the pantry.
All weather pen and pad of paper within reach of the driver. If you see an accident or take part in an accident, its a good idea to write shit down IMMEDIATELY, before the details escape you. Trust me on this.
Extra cell phone in glove compartment, no service. Ideally a rugged model or at least a tough Nokia, they get better battery life than most other phones. You always have 911 access no matter what.
Zippo lighter, even if you dont smoke. Too many uses to not carry around, much like the small multitool.