Bill Gates — Microsoft

Gates left Harvard in 1975 to co-found Microsoft with Paul Allen. For 13 consecutive years (1995-2007), he was the richest person on Earth. Microsoft's current market cap exceeds $3 trillion — the most valuable company in history. Gates has since given away over $50 billion through the Bill & Melinda Gates Foundation, making him both the most successful dropout and the most generous philanthropist in human history. His father wanted him to be a lawyer. The world got Windows instead. Depending on your feelings about Windows, that's either a blessing or a curse.