Super Mario 3D Land to anyone who registers a 3DS and one of 15 games. Between November 27 and January 13, 3DS owners who register their systems and a qualifying game at Club Nintendo will get a free download code for the popular handheld platformer.
If you've already registered your 3DS or you're not from one of the qualifying countries, there'll be no freebie for you sadly. If you qualify, you'll still need to register one of Animal Crossing: New Leaf, A Link Between Worlds, Donkey Kong Country Returns 3D, Fire Emblem: Awakening, Luigi's Mansion: Dark Moon, Lego City: Undercover, Mario & Luigi: Dream Team, New Super Mario Bros. 2, Mario Kart 7, Monster Hunter 3 Ultimate, Pokemon X/Y, Bravely Default: Flying Fairy, and Professor Layton and the Azran Legacy.
Nintendo has more details on how to claim your game here.
As games new 3DS owners should be adding to their collections go, Super Mario 3D Land is right up there. We gave it four-and-a-half stars in our 2011 review, and if you've not got a Wii U to play 3D World on, it's certainly a strong alternative.