I got my shiny new DS lite and with it came a game I imported. As you can see from the thread title, it's called Osu Tatake Ouendan.
A video can explain more than I can, here's how you play it:
The whole game is in Japanese, but that doesn't really matter since the game is not very text intensive.
From what I can work out, you use the stylus to command a group of 3 male cheerleaders in order to help ordinary people out with certain tasks. My Japanese is pretty non existent, but these tasks can range from helping a kid in dodgeball, stopping an invasion of alien robots, winning an election and stoping a meteor from hitting earth. It is bizzare.
If you like games based on rythm and reflexes then check this out. It uses the touch screen very well and there is no other game like it. It's tough though, I can't get pass the last stage in normal mode. If you are looking for a challenge, obtain this game in any way you see fit and give it a go.