I find this light invaluable. the one with the magnet. I grabbed mine at a UPS store for $8. I also carry a mini-mag style light in my bag. I don't like the ones with buttons on the end cap as they always seem to turn on when I put it in my posctket.
[Link: sears.com]

OT, I had a camera taken by TSA in checked luggage. TSA did pay the claim for a new one. I no longer put anything in checked luggage that I value.