A variation of the Seattle Slapjack. Two masturbate facing each other. Upon ejaculation rub the semen into your palm and slap the other person across the face. The first person to slap the other wins.
Guy 1: Hey you trying to get in a Seattle Showdown?
Guy 2: Not right now my girlfriend is coming over.
Guy 1: Dude you're not doing anything else.
Guy 2: Fuck it. Your place or mine.