Geek of the Week: Sugru Uber-water gun.
Every played with moldable plastic? No, burning plastic spoons with a lighter doesn't count.
Sugru is a pretty neat material that you can mold and play around with like play-doh, but will eventually harden into a waterproof rubber. There's tons of stuff you can do with it, but I've always been impressed with the ideas that the company itself comes up with.
Along comes a Sugru water gatling gun. To be fair, YES you can make this thing with Sugru, but it would appear that you most likely also need about $250 parts from a hardware store, an aluminum c&c machine and a degree in mechanical engineering.
HOWEVER....I'd gladly buy one.