We played a fun mod of Super Mario World where controls swap between player 1 and 2. I thought more games should have that mod and decided to do the mod myself at an emulator level so I can try it with any game I want. Controllers 1 and 2 swap randomly every 2 to 9 seconds, so both players have to be paying close attention and you have to be in sync with each other.
We mainly played Mega Man X, but before calling it a night we also tried out some of Pocky and Rocky and Mario 3. You can't hear it well in the stream, but there's a countdown tone that plays before swapping controls.
cptnoremac currently has 20 views spread across 1 video for Mega Man X. The game makes up 4 hours of published video on his channel, roughly 1.71% of Mega Man X content that cptnoremac has uploaded to YouTube.