I vote Feel the Magic. When the DS first released not a sigle game had a good use for the touch screen. Without Feel the Magic, I bet a few people wouldn't even know the bottom screen was touch sensitive. Though some argue that it amy be a little questionable (perverted), it still has mini-games that definitely out-do Wario Ware.
I just need to save up for The Rub Rabbits after the Fall wave hits shore.