“An A-10 pilot failed to re-strap himself properly into his parachute after using a device to pee, only to be forced to eject later in the flight.”
I could not think of a bigger “Oh sh1t” moment that ejecting only to discover you forgot to put your parachute on.
Around 1990 I remember seeing a TV news item about a skydiving instructor who forgot to put on his parachute for the last (obviously) of several jumps that day. They showed his helmet cam footage all the way to the ground, but I don't think there was a soundtrack. He had about half a minute to regret his absentmindedness.