Patapon
I recently picked up this game for my PSP and have been pleasantly surprised by it. Basically you are god to a tribe of walking, weapon wielding eyeballs who have fallen far from their former strength. Naturally they rely on you to help them regain the glory of past days.
The only real catch here is that you can only communicate with your Patapons through drum beats. Each face button on the PSP makes a distinctly different beat and through 4 note beats you can command your miniature army to advance, attack, defend or retreat.
Its a tad difficult at first but once you get the hang of it its really quite entertaining and, even though your commands are limited, theres an extraordinary amount of strategy. You can make different unit types for different situations, go hunting for materials to make new Patapons and theres a handful of minigames to unlock and enjoy as well.
All in all a rather interesting game. Definitely worth a look if you have a PSP.