Elite Beat Agents for just ~$15 including shipping for Nintendo DS. For anyone who hasn't played this game, it involves tapping the screen in certain places to the drum beat of popular songs.
I unfortunately already own it but I definitely recommend it as my sister and I play it all the time :). Very addictive!
This is the US version which means it is in full english and will work on your Nintendo DS (all DS games are region free).
Hope you enjoy!
http://www.play-asia.com/SOap-23-83-c2q0-71-ba-49-en-84-j-70…
pretty good game; the original japanese version has a sequel out there so maybe an english sequel of EBA is in the works