Final Fantasy VI: The Interactive CG Game aka "Final Fantasy 64" (lost playable tech demo; 1995)
In 1995, before Squaresoft (now Square Enix) made their move into the realm of polygonal 3D gaming with their critically acclaimed Final Fantasy VII, (originally released on the PlayStation in 1996, then later on PC), they were experimenting with developing a new Final Fantasy installment for the next-gen consoles of the era. The result of this was a small playable demo, showing off the then-new technology, titled Final Fantasy VI: The Interactive CG Game, though it has come to be unofficially known by many as Final Fantasy 64, as the result of a rumor originally published in an October 1995 issue of GameFan Magazine, which claimed that the demo was taken from an upcoming Final Fantasy game, supposedly in development for the Nintendo 64 (then marketed as the Nintendo Ultra 64). The rumor was discovered as being completely false and unfounded in 1996, however, when Squaresoft announced that the next installment, Final Fantasy VII, was being developed for the PlayStation. In the end, Squaresoft's decision to develop for the PlayStation rather than the Nintendo 64 came about due to a combination of the significantly greater data storage capacity of CD-ROM discs compared to Nintendo 64 ROM cartridges and Squaresoft's dissatisfaction towards Nintendo's stringent content standards, both of which would've significantly impeded Squaresoft's ability to tell the kind of story that Final Fantasy VII ultimately ended up as.
The demo was unveiled at SIGGRAPH '95, (which took place in August), and featured the three playable characters Terra, Locke, and Shadow, (originally from Final Fantasy VI, which was released in North America as Final Fantasy III), showcasing a revamped battle system (which would go on to be largely incorporated into Final Fantasy VII), with the group fighting a rock golem. It ran on an SGI Onyx visualization system specifically designed for intensive 3D modelling, and the characters were controlled by drawing a variety of different shapes with the mouse cursor (each shape representing a different action).
A recording of the SIGGRAPH demo taking place was subsequently released on Square's Preview Extra, a PlayStation promotional disc containing both a demo of Final Fantasy VII and the aforementioned recording, and has since become widely available online. However, the playable demo itself has yet to be released in any form and is largely sought-after by fans of the Final Fantasy series.