With all the disaster preparedness posts going around, one thing that's almost always mentioned is flashlights. A standard-type can be found at the dollar store, along with batteries; quality, so-so. If you're willing to spend the money, you can find something like a Surefire; the least expensive G2 ain't cheap; but it'll blind somebody in a dimly-lit room or outside at night to amazing distances(thanks to the Geek for originally introducing me to these). And their bigger ones? DAMN! they're bright.
However, the one I mostly wanted to mention here is this beast, which doesn't even have a brand name on it:
I found it on Ebay, and the shipping cost more than it did. It's 3.5 inches long, the head is 1" across and holds 12 LEDs, and it runs on one AA battery. It puts out a nice, bright light with no shadows and a little bit of blue tint. I got this thing because I wanted a small light for the motorcycle kit, and it's a new gadget; having been without benefit of artificial light a few times, I tend to collect flashlights.
I've been using this thing for several months, a minute here, a couple there, and decided to see how long it'd last. So about 8 last night I turned it on and left it. When I left for work four hours later it was still bright. When I got home it was still on; not nearly as bright, I'd say enough to let you see where you put your feet at night. So this thing, on the battery that had already had use, put out full strength for at least four hours and was still burning at roughly 1/4 strength after 12 hours. That's not bad at all.
There are a lot of LED lights out there now, some good and some not. So for general use and for emergency kits, you might want to check them out.