Definitely Ataxx. I remember playing it waaayy back when my family went to a restaurant and this was in the bar. I was terrible at it, but I also accidentally played against the hardest AI because I was a kid and had no idea that "Encephalo Man" would be super brainy.
And then later I played Spot and went "wait a sec, they stole these rules!"
And then later after that, it was one of the puzzles in The 7th Guest.
Only the exceptions can be exceptional.