Since we are talking boats...
I've been fortunate to never forget the plug in my smaller boats, but I did something stupid on the large boat:
Before leaving the marina, I went down into the engine compartment to check the oil, coolant, and general condition. I also checked that the fuel valves were all in the normal position: port engine fuel feed and return to the port fuel tank, and vice versa.
As we left the marina, the starboard engine quit. It was touch and go for a bit, but I managed to make my way out on one engine. When I went back into the engine compartment, I discovered the starboard engine feed valve in the off position. I switched the valve back on, primed, and started the engine, but I could not figure out how I missed this. A few months later I figured out when I was climbing out of the engine compartment: my jacket snagged the starboard fuel valve handle, and rotated it to the off position. Since then, I made it a habit to look at the fuel valve panel one last time, after climbing out of the compartment.