As of late i've been addictively playing Monster Hunter 4U and Final Fantasy Theater rhythm: Curtain Call for the 3DS.
Monster hunter is a great game and possibly the best in the series. The game has a ton of new monsters to hunt (from older games in the series and a fair smattering of new ones), and the gameplay is as solid as ever. The new additions (from the revised Palico system, new weapons, vertical gameplay elements and mounting/riding monsters) all add a fun new dimension to the game, and using the insect staff to polevault into the air to knock down a giant spider that wears the corpse of a wyvern on its back from its web is extremely satisfying. Of course, the game retains the 'classic' monster hunter gameplay, so while the controls are veryprecise, you still have the firmnes and animation rigidity that can turn a lot of people off of the game.
Curtain Call is a final fantasy rhythm game where you have to use the stylus (Or buttons) in accordance with the music. The game has over 200 base songs in it from across the franchise - plus a boatload of DLC from the final fantasy series and other games (Nier, Xenogears, secret of mana, Chrono Trigger, and more), and you make parties/'quest' with final fantasy characters you can unlock. It's basically a final fantasy fanservice game, but the series does have a lot of good tracks for that.