Pet Rock
If you’ve ever collected rocks as a kid and imagined them as pets, then you could be a millionaire by now. Someone else beat you to success with this idea, though. Sometimes, weird inventions seem to have no real purpose. Inventor Gary Dahl got rich during a conversation in California, when he said he didn’t have to worry about dogs or cats destroying furniture because he had a “pet rock.” He was joking, but then decided to take it seriously. Eventually, he monetized his pet rock, and sold around 1.3 million to 1.5 million pet rocks a month. He earned over one million dollars before the fad died out (Mental Floss).