Shot for shot is a game in which two males try to prove their manliness.
You would take turns striking at one another; the hitter can hit as hard as they like, and the receiver cannot move away to the dodge the blow. Generally played by hitting the arm, but anywhere is acceptable. Although the game is viewed as INCREDIBLY stupid, the winner is seen as "badass" due to the violent nature of the game.
Guy1: Dude, let's play Shot for shot.
Guy2: Shit, I can't even move from last time...