Patapon is a funny little game (according to what I’ve seen in gameplay videos, unfortunately I do not own a PSP) by Pyramid / Japan Games where you command a warrior tribe with drum signals. Rythm and sequence of the drums dtermine the maneuvers. especially the pictographic artwork is great.

To try it out there is a  Flash-Demo, which is a kind of simplified tutorial.

LocoRoco by the same creators looks interesting, too.