The mac-daddy of Redneck Engineering:

Neil Armstrong, the first person to set foot the moon, and Edwin E. “Buzz” Aldrin Jr., his fellow astronaut, accidentally snapped off the switch of a circuit breaker, and found they could not take off without it.

Aldrin then jammed a ballpoint pen into the hole where the switch had been, allowing the astronauts’ lunar module Eagle to leave the surface of the moon.