David Baszucki

To millions of tweens, Baszucki is better known as “Builderman,” his username on Roblox, the addictive video game/social media site he founded and runs. The company, which went public in March, provides tools to kids who then use them to make—and sell—their own games. The company doled out more than $325 million to developers last year for their services and grew its user base by 85%.