DarkSeed (found NeoGeo prototype game; late 1990s)
Screenshot of the character select screen.
Date found: 10 Apr 2016
Found by: NeoTurfMasta
In 2016, neo-geo.com forums user NeoTurfMasta released a dump of a ROM of a NeoGeo cart he won from Yahoo Auctions Japan. At the time, virtually nothing was known about it. The game appears to be in an early beta stage, with most artwork present but not much else. Kengo Asai has come forward as the producer, saying that its development name was DarkSeed. 
He had noted that the information on the physical materials of the cart match up with Voltage Fighter Gowkaiser, which was theorized to mean that the game was developed by Technos Japan (the developers of that game). Technos itself was not involved, but many developers worked on both games. 
The game features about 12 characters, most of which are unfinished to varying degrees. Some characters' sprites feature animals as a method of attack. The entire system seems to be inspired by Dungeons and Dragons, given how everyone is sorted into a Neutral/Lawful/Chaotic system.