I know Neil Armstrong was an Apollo 11 guy, but Apollo 13 still gives you a lot of insight into the sort of danger astronauts willingly put themselves. Landing on the moon is an insane accomplishment, and there was so much that could have gone wrong.
Unlike your Alien and Star Warses and whathaveyou with aliens and bad guys, Apollo 13 wonderfully, creepily portrays the insane stress these kinds of missions involved, and teases at the utter horror of dying alone (the last one to die, anyway) in the cold, dark, void. It really makes you realize what these guys had to be ready for. I mean, read this speech Nixon would have given if the Apollo 11 crew had been stranded on the moon and left to die. Horrifying. Oh, and Apollo 13 is also just a really good movie in general. Watch it. [Netflix, Amazon Instant]