Fame
Are there famous sports agents? There are, but they're famous only within the field of professional sports, really, not to the general public. People like Scott Boras (who represents Alex Rodriguez), Fernando Cuza (who's on board with David Ortiz), and Rob Pelinka (Kobe Bryant) are well known in their profession, but not to most.
These guys make a lot of money, and if they've chosen to show off some of the philanthropic endeavors they've undertaken (if they even have any philanthropic tendencies), maybe their arena of fame would be wider.
Note: You'll never be as famous as the best, most highly sought-after player you represent, so if it's fame you're after, train to become the new Miguel Cabrera or Yao Ming and get your own agent.