One of my favorite games.

User Rating: 10 | Rhythm Tengoku GBA
I just stopped playing a little bit of the drum lesson session. In the drum session minigame that you unlock, you have a little guy playing the drum set to a specified loop and when you feel comfortable and have memorized it, you can jump in and if you repeat his loop for 5 consecutive times without messing up, you pass that play test. Basically you feel like you are learning how to play the drums because you have to keep a different Rhythms with different fingers and this can get really challenging and could be impossible for people without rhythm.

Aside from the drum game, the game feels sorta like a wario warez game. Lots of simple graphics and cute art that is very memorable and an instant classic. The music will play for hours after you have turned off the GBA in your head. I would recommend this game to all but if you know that you are not good at keeping a rhythm, you might find yourself giving up half way through because of the difficulty. Other imports I recommend:
Jump! Ultimate Stars
Bit Generations Dot Stream
Yakuman DS wifi (online mahjong with mario and buddies)
among others