What kind of list would this be without Neil Armstrong? A dumb list, that's what. Armstrong was the first human to walk on the moon, fulfilling a cross-cultural dream older than the written word. As Commander of Apollo 11, Armstrong was lucky to enjoy a relatively problem-free lunar landing, but that doesn't mean all his missions were so "easy." Like Gagarin and Cooper before him, Armstrong had his own mettle tested when Gemini 8 (launched in 1966) went completely bonkers on him and his crew mate David Scott. Gemini 8's mission was to achieve the first docking of two spacecraft in orbit, but when the ships began spinning out of control, Armstrong and Scott were forced to endure a real-life Gravitron...in space. Though NASA notes that the astronauts' physiological limits should have been surpassed, Armstrong resisted blacking out and managed to override the system, aborting the mission in order to save his and Scott's life. We'll always miss you and your iron will, Neil.