There are many factors which make a fighter a valuable commodity for the UFC which go beyond simply what they can generate in pay-per-view buys or live gates.
Those are fighters which act as ambassadors to the sport, have crossover appeal and can hype a fight better than any other: fighters who have become icons of the sport, have generated massive fanbases and come to define an era in MMA.
Some of the most notable, most memorable and most watchable have made this list of men the UFC will sorely miss when they are gone.