From now until June 30th, if you register three of eight specific games at Club Nintendo, you can receive a fourth from the list for free.
The list of eight 3DS games are:
"¢Castlevania: Lords of Shadow "“ Mirror of Fate
"¢Monster Hunter 3 Ultimate
"¢Luigi's Mansion: Dark Moon
"¢Fire Emblem: Awakening
"¢LEGO CITY Undercover: The Chase Begins
"¢PokÃ©mon Mystery Dungeon: Gates to Infinity
"¢Donkey Kong Country Returns 3D
"¢Animal Crossing: New Leaf
If you're living in Europe and have a 3DS, there's no time like now to experience some of the better games of the 3DS library.