I don’t like to wear caps, but here’s one that would make an exception: the Solar Light Cap.
It has a solar panel stuffed somewhere in it and two LED spotlights that provide enough light so that you can read or see anything when in the dark (I first wrote “when in the dork”, hm).
The solar panel charges with sunlight, of course, so you have to take the cap out on a sunny day if you want it to work. About 2 hours of direct sunlight are enough to make the LEDs stay bright for up to 18 hours!
But what if it rains on it, won’t the panel and the electrical stuff go bye-bye? Well, no. The cap is waterproof. So you can even go scuba diving with it, though I’m not sure who would actually do that.
The Solar Light Cap costs $35 and it can be bought from ThinkGeek, one of my favorite websites!