Splatoon.
My understanding is that it's Call of Duty, but with ink and waterguns rather than guns and bullets. The objective is to cover the map in as much of your team's ink as possible. Which ever side has the most colour, wins. You can also turn into a squid to move fast over your colour ink, allowing you to swim around faster, but you can only do that in your coloured ink and you can't shoot whilst doing it. Jumping out the ink turns you back into a human/child/Japaneseman'sfantasy.
Hope that makes sense... that's my general impression of it. I personally might get a WiiU just to play it; it looks fun.