robotech: the motion picture
An unmade live action film adaptation of the first arc of the Robotech mecha anime adaptation from the 80s.
The movie was going to be based on the Macross Saga and had some pre-production art made for it. Work on the project started in the late 2000s.
It was being produced by actor Tobey Macguire (himself a Robotech fan). The adaptation is currently in development hiatus limbo.
Some of its planned effects and design elements and/or styles are rumored in Hollywood circles to have ended up being used in other productions like the later live action Transformers films by Michael Bay and the Pacific Rim movies.