During Apollo 11, a circuit-breaker switch inside the Lunar Module Eagle broke, preventing the astronauts from properly arming the ascent engine.
Buzz Aldrin used a felt-tip pen to push the remaining mechanism and activate the circuit.
It worked — helping Armstrong and Aldrin launch from the Moon and return home.
That tiny pen and the broken switch later sold for $857,600.
A pen worth less than a dollar helped save a mission that changed history.