Vectorman (found builds of unfinished PlayStation 2 platformer; early 2000s)
Vectorman is a cancelled 3rd person shooter that was in development by Psuedo Interactive, targeting a 2004 release. It was supposed to be a reboot of SEGA's Vectorman series and was radically different from its predecessors. Due to a bumpy development cycle, the game was cancelled soon after its reveal at E3 2003. The only material that is out to the public is gameplay footage of a prototype shown at E3, and concept art that surfaced years later. There were also other prototypes pitched.
According to a Retro Gamer and Ign interview, Pseudo Interactive pitched demos to SEGA for a new Vectorman game, with one of them being similar to Smash T.V. This demo involved Vectorman running through time, with the music being techno, and had shooting gameplay. SEGA were impressed enough by these demos that they greenlit a prototype. At the start, the project was more in line with the past two games, with one of the things kept in tact being Vectorman's orb design. This more faithful approach lasted 3 to 4 months until SEGA switched producers, thus leading to a focus test of the prototype that didn't go well. The younger audience during the test were confused by Vectorman's orb design and were not familiar with the series. This caused SEGA's producers to ask for changes around the new year of 2002. A producer suggested taking inspiration from Socom and Halo due to their popularity at the time. After 8 months, SEGA cancelled the project in August 2003. The reasoning for cancellation seems to have multiple different answers with none being absolute. These answers range from SEGA realizing they changed the series too much, SEGA of America were about to have layoffs and were disinterested in their retro IP after Toejam and Earl 3 underperformed, to the game still being in kind of rough shape at the end of development, and it was easier to cancel it than to finish it for release according to a YouTuber named Snack Cabinet Gaming who claimed to have talked to the developers of the game and had info that matched with the info revealed in the Retro Gamer interview. 
One of the plot points of the story would be about Vectorman losing a previous battle, and then being rebuilt. Another plot point would involve you trying to save Gamma 6 from an Orbot named Volt. It would have you begin in an environment similar to Ord Mantell which would have Vectorman travelling through a crashed ship that was ascending. The gameplay would have destructible environments and multiple weapons and upgrades to choose from. Vectorman would also have a grappling hook for traversal.  
On December 30th, 2023, multiple builds of the game have been found by SEGA Dreamcast Info.