Not a game, but it only goes on sale once every year or so. A fantastic flash-card application which supports community deck sharing and cross-platform syncing. Requires a PC for setup and some advanced features, and the PC app is free (and so are all of the community-created flash card decks). Highly recommended for any students studying a foreign language or a vocabulary-intense subject like Biology or Chemistry. App info is currently processing and/or the app is not yet fully available for sale on the US App Store.
