This water bottle from Solight does double duty as a solar-powered lantern. The LED light charges up while you're hiking or fishing or whatever, then at night you can hang it on a tree or set it on a table or on the floor of your tent. It lasts up to 8 hours on a single charge. I find that every extra item I have to carry feels like lead at the end of a long day of hiking, and I would no sooner do without a light as I would without water, so for me, a water bottle/lantern combination is appealing.

Available at various outdoor supply stores (and at Gaiam, which sells it for $29).