The slinky was invented by Richard James.
(It was a fortunate accident. Mr James, working as a naval engineer at the time, noticed the interesting flip-flops of a torsion spring bouncing across the floor. After the war he and his wife began to manufacture them as children's toys. According to one estimate more than 300 million Slinkys have been sold worldwide. The only change in the original design has been to crimp the ends as a safety measure.)