Peter Thiel, renaissance man. Suzie Katz via Flickr It isn't easy to pinpoint exactly what Peter Thiel is most famous for. His interests range from the mundane (online payments) to the fringes of scientific thought (immortality and floating cities).

He's a libertarian. But he has also funded the secretive data-mining company Palantir, which works for the FBI and the CIA.

Check out some of his amazing quotes »

He co-founded PayPal and acted as its CEO before the company sold to eBay for $1.5 billion in 2002.

Since then he launched the global hedge-fund Clarium Capital and the Founders Fund, a venture capital firm. He was Facebook's first outside investor, making him a billionaire when the company went public.

He supports the Methuselah Foundation, whose goal is to reverse human aging, and the SeaSteading Institute, a libertarian group founded to create independent floating cities in international waters.

He's also launched the controversial "20 Under 20" initiative which gives 20 teens $100,000 to drop out of college for two years to pursue their own tech projects.

He is one of the most original, controversial thinkers in tech today.