Mario Tennis Open, otherwise known as Mario Tennis 3D, just released a new trailer showcasing a ton of the game's "extra" modes, in addition to the new Mii customization system. Old school fans will probably go gaga over "Super Mario Tennis" mode, which features old school levels from the original NES game, but the usual stable of Tennis mini-games are included as well.
I'm not all that excited for MT 3D (mostly due to the fact that I played like 500 hours worth of Mario Tennis ), but it's still shaping up to be an awesome addition the 3DS is year. While the Wii is on the way out, the 3DS is ramping up in a big way in 2012 -- when you think about it, in just a few months we're getting Heroes of Ruin, Theatrhythm, Pokemon Conquest (DS), and Kingdom Hearts 3D.
Mario Tennis Open Special Games [YouTube]