Here’s an unlikely one for you. In the 1980s, Lonnie Johnson was employed at NASA helping the space program develop new thermodynamic and controls systems. When working on an air hose, he tested a new nozzle design that he’d been working on, only to find that it propelled far faster than was necessary. Johnson took the concept home and tried to find a use for it, and eventually he discovered that pushing water through the nozzle was a huge improvement on the traditional squirt gun. In 1991, he and a partner patented the design, found a manufacturer and the Super Soaker was born.
Photo credit: Flickr user clappstar via Creative Commons.