Pericles, Socrates, Cicero, Abraham Lincoln, Mahatma Gandhi, Winston Churchill, Adolf Hitler, Franklin Delano Roosevelt, John Fitzgerald Kennedy, Martin Luther King Jr, Nelson Mandela and Mike Soper would be a good short list but it's relatively Western and specifically American centric. Personally, I would go with Abraham Lincoln but I can see arguments for most of them. I think Hitler is definitely overrated just because people see him going crazy in a language they don't speak over some dramatic dubbed music on youtube.