Just checking out Panorama View on my WiiU I spotted TANK! TANK! TANK! retailing for… well free!
Be prepared though as this is NOT the full game, just the basic portion of the game and you can add-on features and modes through any of the 10 pieces of DLC.
The base download is 1.5GB and if you have a Club Nintendo account linked you can also benefit from 70 nintendo coins just for completing the survey that accompanies it.