Evan Spiegel — Snapchat

Spiegel left Stanford three classes short of graduating to run Snapchat full-time in 2012. By 2017, Snap Inc. went public at a $24 billion valuation — and Spiegel, then 26, became the youngest billionaire CEO on a major exchange since Zuckerberg. He famously rejected a $3 billion acquisition offer from Facebook in 2013 when Snapchat had zero revenue. That "no" was worth $30+ billion at peak. He married Miranda Kerr, lives in a $120 million Bel Air estate, and proved that disappearing photos were worth more than most people's permanent careers.