This year I twice got the rich challenge to perform Alexander Schuberts wiki-piano.net. The piece is not actually written by him, but rather by anyone who chooses to sign up and contribute. Performing the piece can involve anything from playing, singing, speaking, (in one case) miming and dancing to, well, really anything the current editors thought of. Anyone can edit the piece at any time, so when performed the pianist chooses a time version and locks the score. This means every version of the piece is quite different. The video from the ZKM performance is available here.