The Journeyman Project: Pegasus Prime

Originally announced as a "Director's Cut", It was released solely for the Power Macintosh by Bandai Digital Entertainment in North America. It contained a 4 disk set which required disk swapping during gameplay. There were plans to port the game to the PlayStation (with publisher Acclaim Entertainment) and Sega Saturn in the U.S., but these versions were never released. As a result, original disks of the Mac-only game have been very rare to find.