Here are two more unused designs from the late 1980s.
The "Sewer Scraper" was one of my designs for the second year of the Playmates TMNT toy line, and I was disappointed that it was never made. I thought it was cool, and I would have enjoyed playing with it! I think it would also have been fun to use in the TV show.
The "One-Mutant Assault Helicopter" was intended for use by the Shredder's mutant henchcreatures -- I think that may be Rocksteady in the cockpit. This design was also never made into a toy. -- PL