One of the titles I saw at GDC that made me think Nintendo is on to something with the DS was Electroplankton. The
thing isn't a game, unless you define "game" as "something that is fun." The product uses the DS' mic to let you see
your voice translated onto the screen in a million ways. It's a little like Dreamcast's Seaman and PS2's Dance Dance
Revolution.
Check out the clip to see what I mean. Creepy and appealing stuff.
