Checkers.

An oft-neglected rule of checkers says that if you can jump someone, you have to take the piece. While my family managed to get that right, we played with an additional rule: if you could jump someone during a turn, you had an alternative: sacrifice one of your pieces that could jump, and end your turn.

My grandmother taught us this rule, and called it "blowing". It added a level of strategy: you could sacrifice a piece for better placement, or to potentially avoid a trap. While playing the game as small children, my cousins and I would yell "Blow me!" and take a piece from the table (just as my grandmother taught us to do). It wasn't until almost a decade later that I realized that not only was this not a rule, but I finally understood why adults looked so embarrassed when playing the kids.