Was there a project that employed some custom shaped buttons for the CP?
Nearly every CP I've ever seen uses the standard round buttons eg happs.
Atari restorations or wannabes use the volcanoes.
CrapMAME qualifiers use the squares.
Then there are a few oddball ones from the arcades eg Street Fighter and Pop 'n' Music.
But was there ever a cab project that used custom buttons? I recall someone posting about a round button that sported two halves, but the OP later realized it was a bit too large to fit in place of a standard arcade button.