Gundam Transformer/Flight & Operations Unifications Reactors (GT-FOUR)

Developed by the Earth Federation Air Force, it was a prototype for a transforming Mobile Suit. Unfortunately, the frame wasn't strong enough to transform repeatedly and was never officially deployed. It's data though was used to make the Ashimar and Gaplant years later.

(It may be a super obscure Gundam, but I like it. Had trouble figuring out a proper scenario for the longest time, so it's Operation Odessa but probably suckier. Small spoiler, but you are not the only Gundam fighting.)