How about a Vex Robot fire-fighting contest where Vex robots follow a maze representing the walls of a house or building a la Trinity Fire-fighting Contest held in Connecticut each year, except with a twist. No weight limits, no size limitations, anything goes to put out the fire (candle).
Another twist to this contest is a class of Vex Climber Robots that can climb ropes or walls or sides of houses and buildings for rescue operations.