Nintendo of Europe are offering a free game to those who purchased any 3 of these recent Nintendo 3DS games and register them to their Club Nintendo account. Check the link here for more details: LINK
I've already managed to claim mine, which is surprising based on how niche I thought some of the games I had were. For those of you interested in which 3 I had already - MH3U, Fire Emblem and Castlevania.
Eligible Nintendo 3DS games for So Many Games! promotion
There are eight Nintendo 3DS titles in this promotion: