Solo Scientific's $40 Tinder HOT Box Solar Fire Starter is air- and water-tight, uses no fuel, or batteries, and keeps your dry tinder dry in transit. It's machined from aircraft aluminum and wights 4oz. Not much use for getting dry in a snowstorm or thunderstorm, but still awfully handy.
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.