Got to agree with Igor. He was rumored to be slated for the last ADCC but he never came.
I'm going to throw one out there that will likely get me flamed, but here goes: RICKSON
The confidence in his face, his calmness during the fight, his technique (granted it was before people learned sub defense) It too bad more of his legendary NHB fights in Brazil back in the day weren't caught on film, or better quality. (not all 400, of course

)
We'll probably never know why he didn't fight Saku. Greed, fear, arrogance, the death of his son, who knows. All have been debated and argued to exhaustion.
For me, it was the greatest fight that never happened, even if Wandy/Chuck never happens.