Slinky
Slinkys were some of the most entertaining weird inventions as a kid. You’d watch a coil move down a flight of stairs. Even though it sounds boring, it was actually a huge hit. It was invented by Richard James in 1944, and slowly gained traction. Monica Smith, the head of exhibitions, said, “the Slinky was something that he saw happen and he thought it was cool. It wasn’t an obvious idea for a toy. It wasn’t something he was setting out for—it’s more serendipitous than that. He kept an open mind and found a different use for it.” Slinky means “sleek and sinuous in movement or outline.” With what started as a $500 loan quickly turned into a profitable invention that made them rich (Smithsonian Mag)