The players of Crossbows and Catapaults each started out with a little treasure of some sort that they built a castle around using plastic bricks. You and your opponent would then take turns either launching ammunition at each other's castles with the catapaults or shooting bricks with the crossbows.
My family literally spent HOURS sprawled out on the living room floor, cheering on whoever happened to be playing. In our house, the rules were that the "winner moved on"! It made for some LOOOONG nights of game-playing!