First thing you'll need, would be the NGC Controller, any would do fine but the official is the recommendation. Original (wired) or Wavebird (wireless) are the best GameCube controllers. And lastly, this little device to connect the NGC Controller to make it recognisable as a Wii Classic Controller, which you'll plug via the Wiimotion Controller. This is also usable for the Original Wii without the GameCube controller port. Watch this video for any concerns on how to make the connection work properly, if you're having issues. Enjoy playing Wii U with the NGC Controller.