The piano trio thread turned up some interesting choices. How about "obscure" (or at least fairly obscure) horn trios?
Anyone can choose trio records by Sonny, Ornette, Cecil, Air, etc. if they choose to, but I assume that most already know about those.
I'll start with a few:
Roy Campbell Pyramid: Communion
Don Ellis: Out of Nowhere - I like this one better than How Time Passes.
Louis Cottrell Trio: Bourbon Street