The “crackpot” term is often used by @dougselsam. It refers to both crazy designs and conformist attitudes.
I will try to produce a design as crackpot as possible. I may have done this in several (if not all) previous messages.
So two counter-rotating bladeless rotors rotate two balloon filled with helium, using angle gears, that produce thus some Magnus effect. The force is used during the yoyo reel-out phase. During the reel-in phase the direction of rotation of the rotors is reversed.
I would guess some methods now well reputed will enter this rubric.