I used to have as Streamlight Twintask 2L, and a Minimag in the glovebox.
Now, I have a Nuwai TM-115X under the driver's seat (3-watt, 2xCR123, two-stage light). It's pretty much a clone of the Streamlight Tasklight, but goes from off to low to high to off, which I prefer, and it's cheaper.
In the glovebox, I have an Eternalight Ergomarine (thanks Matrixshaman) and a Nuwai TM-317X (1-AA, .5-watt, hi-lo), which is good for map reading on low.
And finally, an Infinity Ultra with a Jakstrap headstrap in teh first aid kit.