If you're into nature and walking around outdoors, even jogging, the lightcap is the ultimate gadget for you. I go jogging at night a lot and don't like lugging a lot of crap around, but sometimes I go down streets without streetlights and it gets annoying after tripping over so many branches and bushes. The Lightcap from Simply Brilliant fixes that. It's a 1 liter water bottle (the jug kind you get for hiking, not a sport bottle) with a light built into the cap. A solar cell inside the cap charges the cap up during the day so when you go hiking, running, or whatever at night, you have a light to guide your way and don't have to bring any other things with you. 12 hours of sunlight will net you 8-10 hours of normal light with even more if you use the red LED mode. You can score one for a cool $24.95.
Lightcap by Simply Brilliant [Treehugger]