It all started with an accident. Late one night, while experimenting with a jet pump and a nozzle for a refrigerator cooling system, Lonnie Johnson shot a stream of water clear across his bathroom. Where some people might have seen a mess to clean up, Johnson saw an opportunity. Thus was born the mother of all water guns, the Super Soaker.

After leaving NASA’s Jet Propulsion Laboratory in 1982, Johnson built the prototype for what would become the Super Soaker in his basement workshop. He had several false starts, but “a good challenge keeps me going,” he says. Although he applied for his first patent on the water-gun design in 1983, it wasn’t issued until 1987. About that time, he decided to leave the Air Force and work on several private projects, “any one of which might have made it,” says Johnson. But when he left the Air Force, they all fell apart. “There I was with no home, no job and a family of five to support.”

He returned to JPL and began shopping his water gun to toy companies. After two frustrating years, he hit the jackpot with Larami Corp. By that time, he had already sunk close to $15,000 into the project, and his licensing check was only $5,000. But Larami’s goal was to produce 100,000 water guns the following year. In 1990, despite little advertising, the gun — first christened Drencher — became a sellout. Renamed the Super Soaker in 1991, Johnson’s invention became the number-one toy in the country.

Larami has since been sold to Hasbro, but Johnson, who lives in Atlanta, still works with the company on updating the Super Soaker. His quarterly royalties have made him a millionaire, giving him the wherewithal to start his own research-and-development company, which is currently working on energy technology. Before his invention took off, “I had days when I’d stop and think, Why is it taking so long?” says Johnson. “But I never thought about giving up.”

Kiplinger’s Personal Finance Magazine