I believe that some of the very best basenjis likely finished their CH and retired to the couch - it is not necessarily the best basenji that wins the most best in shows BUT the best campaigned basenji that being shown extensively. There are many of us on the list that show - finish a dog and no one may see the dog again until a time or two at veteran - that does not mean that the dog is not the quality of a top winner - just means we don't want to - or don't have the money to travel the country 365 days a year.
There are dogs that are significant because of the traits that they passed on to their get, there are dogs that are significant because then consistantly produced good (insert feature here) . There are dogs and bitches that contributed things that we have to work around. There are several things that I think of so I"ll take a stab at it.
Re-up, Smooth operator of Woz, Reliant Inferno - are a few oldies that I think offered some significant things to the breed.
Johnny - brought great visibility to the brindle coat at a time when few had seen it (didn't hurt that he was a pretty nice dog too)
Nate - added some refinement to some lines that maybe had gotten too cobby
Bravo - in the show ring - pushed the envelope in BIS when few looked at the basenji as a Best in Show Candidate.
Mira - beautiful bitch who produced consistantly Tootsie who appears to produce consistantly with different sires.
Geez there are tons more - if any of you still have your old 'years of the american basenji' I am sure you will find tons of animals in there that you would like to consider - have no idea how to reduce to just a few.
In any event that's a few of the animals that sprung to mind immediatly