Quark AA2 (now called a Quark QP2A) and a Zebralight H51 headlight in both cars. I keep each of them loaded up with rechargeable eneloops and 4 lithium AA batteries as back up in each car too. Having lights in our cars has come in handy several times in the past (so far for fun reasons and not for emergencies.) Truthfully, the real reason I have these lights in our cars is mostly for fun. In an emergency, I have lights on me already, so I'm prepared (lightwise) well enough I guess. But, when we show up somewhere at night, I like having the extra lights in the car so we each (wife & kids) have a light to play with....like at a friends house, or in a park, etc.
In my pocket is always a Zebralight SC52w, and on my keychain is my ITP A3 EOS (AAA light.) I have a spare lithium AAA on my keychain and a spare lithium AA on me too for the SC52w. I recently discovered that the SC52w will also run on a single AAA battery without loosing conectivity (even when shaken very hard)....cool.