Big Wind - The most powerful fire engine of the world: 2 MIG-21 jet engines mounted on a T-34 tank base
It's for extinguishing oil well fires, owned and developed by MOL, the Hungarian oil conglomerate. It was used in Kuwait after the Kuwait-Iraq war, here is a video of it in action: https://www.youtube.com/watch?v=uyGDxglTVgA
It's still in use and maintained, the base was replaced with newer tank recently, as it was hard to find replacement parts for such an old model.
I saw this thing work in the documentary about the Kuwaiti oil fires the first time I ever went to an IMAX theatre. For some reason that has stuck in my mind for nearly 30 years.