Figures it would take a rocket scientist to invent one of the greatest water guns of all time, the Super Soaker. One day in 1982 Johnson, an aerospace engineer who loved to tinker at home, was working on creating a heat pump that used water to cool down instead of Freon. That device led to one of the most popular toys ever made. The Super Soaker generated $200 million in retail sales and turned Johnson into a millionaire. He’s now using his fortune to develop energy technology.