Che Guevara
"The guy's face is shorthand for 'I'm against the status quo.' He's politics' answer to James Dean, a rebel with a very specific cause."—David Segal, The Washington Post
Ernesto Guevara (1928-1967), best known for his nickname "Che", was an Argentinian Marxist revolutionary best known for two facts: his active role in the Cuban Revolution (in which he helped Fidel Castro to seize power), and making a profitable market of people who bought T-shirts with his face on them after his death. He also took part in the Congo revolution, but it wasn't successful.
Defending a socialist cause and being executed at a young age, Che Guevara has evolved into a symbol that represents both "civil disobedience" and "political awareness" (The Other Wiki has a full article about it). More often than not, he is also used as the "Romantic Expression" of Guerrilla Warfare: a tough but well-intentioned guy, willing to fight injustice (and american imperialism) over everything (one example is Metal Gear Solid Peace Walker).
Lots of books, quite a few movies, and even an SNK Metal Slug-ish videogame called "Guevara" (dolled up in the USA as Guerrilla War) have been done about him.