Anybody here who's familiar with arcade 1943 knows that there are 16 stages in the whole game. I got haflway through Stage 16 on 1 coin. Hve pics of the score, and a witness to the fact. Notwithstanding that the score resets when you continue (IIRC). That was a bitch to do, and even though the machine is in the basement, I still think it may even be a few more years before I attempt that one again. Probably a couple more, I'll have to reflect a bit longer.
Being completely unable to pass Stage 2 on arcade Gradius III comes to mind. Impressive in a negative way, eh? God that game is ridiculously hard!! (or maybe it's just me)