Grid style arrays of buttons for music are quite popular with the release of the Monome, spawning many imitations such as the Arduinome. Patrick Flanagan has gone one better and created his controller, the Meganome, from scratch using arcade-style buttons from Adafruit.
Patrick, who creates music under the name Jazari, is no stranger to DIY controllers, as he created and performed with his horn claw before creating the Meganome. Patrick has included a few sensors, including a PlayStation analog-style controller, a proximity sensor, endless encoders and pressure sensors. The thing is pretty amazing, and the case it's mounted in looks excellent. It definitely looks of commercial quality.