It's Duck Hunt! No, not the infuriating NES game of the same name.
This creation models itself after carnival-style shooting gallery games, where a number of "ducks" (in this case, minecarts) travel back and forth across a playing field, while the player tries to shoot them down with a bow and arrow. While the game lacks any sort of formal scoring system, it's still a pretty clever innovation, especially for being built both out of redstone only, and not taking 3 weeks to construct.
As with his other creations, Mumbo goes over the ins and outs of putting the shooting gallery together, so you can make your very own. Enjoy!