Carl Icahn, a corporate raider and a private equity investor, was educated at Princeton University and New York University School of Medicine, but left prior to graduation.

Not becoming a doctor turned out for the good for Icahn, who is a billionaire financier with an estimated net worth of $14 billion.

Icahn calls himself an activist investor and is leading a shareholder revolt at Yahoo hoping that the Internet giant will sell out to Microsoft. He has launched a proxy fight to unseat Yahoo's board.

Image: Billionaire financier Carl Icahn, seen with comedy club owner Caroline Hirsch. | Photograph: Mat Szwajkos/Getty Images