M-Audio Hammer 88

Great if you want lighter keys. Works flawlessly. The main problem is that it cannot power an iPad when used with an external power adapter. This is really irritating since I use the iPad as the sound source and it needs to be disconnected and charged somewhere else. Although there exist adapters that can charge the iPad while connected to the keyboard, they require additional wires and power adapters (and tend to stop working if permanently connected).