What are the speakers you very rarely find in the Used market(Audiogon or Anywhere)?

GOOD ONES.

Someone still hankers for a pair of ML Monolith IIIs?  I sold mine 20 years ago and good riddance, slow bass, directional, limited dynamics.  Replaced with Legacy Focus.  Music preference is opera, jazz, classical and pre-1980's pop while wife also wants to enjoy heavy metal and raucous rock.  Focus speakers suit everything while Monoliths had limited appeal even for my tastes.  Generally rarely seen are Acoustats (I had 2&2s), especially Xs which were deemed the big coffin speaker by my late wife. 

Have seen one US pair of Devore Gibbon Xs in 3 years...sold in like 48 hours.

Sony SS-AR1. Even more rare are SS-AR2 speakers. 

U-Vola seem to be pretty rare https://www.ebay.com/itm/323737117992