My vote would have to go to the one I had back in the late 70s, the Pioneer RT-707. It might not be the gnarliest, but it just may have been the most unusual looking.
https://www.hifiengine.com/images/model/pioneer_rt-707_open_reel_tape_deck.jpg
https://www.hifiengine.com/images/model/pioneer_rt-707_open_reel_tape_deck.jpg