The revelation of the WiiU, which has mostly been disappointing in terms of 'real' classics until now. Kind of a small game for an 8th Generation game, but it was an idea that should have been done generations sooner. Obviously, it would be impossible for it to have existed sooner in this way due to the WiiU's Gamepad, which is finally utilized in a vital way. But still.
Like the name says, the game has the player create their own Super Mario levels. Using standard building blocks, enemies and platforms that can combine in a near infinite amount of ways, players can create almost anything they can imagine and there have already some very good levels here and there. Besides building you can obviously play other people's levels and developer-created levels which include some interesting new ideas.
The building's what the game is all about to me though. Being one of the best editors I've ever used combined with a game-series that I'm usually quite fond of, I like taking my time to create something I'm satisfied with. The game is still missing a couple of features though, and as such would actually be one the few games I would buy additional content for.