Most events can be customized further in the Racebox, a game mode that allows you to create custom races and grids that can be exchanged with other players. The object in the single player mode is to get ten kills. In this game mode, you take damage at a much quicker rate and cannot absorb your weapons (pushing the corresponding button only gives you a brief shield).
This mode has several special super-weapons unlocked for it such as the disruptor and shiruken.