39. Bill Gates
The man who founded Microsoft and helped make personal computing accessible to the masses quickly became the wealthiest man in the world (although that title no longer belongs to him). In addition to pioneering own computer software, he established the Bill and Melinda Gates Foundation to help alleviate poverty in developing countries. Today the Gates Foundation is the largest private foundation in the United States and has been a part of significant healthcare initiatives, including the eradication of polio.