From
http://www.gameinformer.com/b/news/archive/2013/02/14/nintendo-offers-3ds-xl-free-game-deal.aspx :
As part of its Nintendo Direct, the company revealed a deal designed to entice gamers into picking up a 3DS XL. Players who pick up the system and one of two games will be able to pick an additional game at no extra charge.
You'll need to pick up a 3DS XL and a copy of either Pokémon Mystery Dungeon: Gates to Infinity or Luigi's Mansion: Dark Moon. After registering the products, you can then select a free copy of either Super Mario 3D Land, Professor Layton and the Miracle Mask, Art Academy: Lessons for Everyone!, Star Fox 64 3D, or Freakyforms Deluxe: Your Creations, Alive!