Fame
There have been maybe ten famous FBI Special Agents. Maybe. If you're trying to take down an infamous bank robber or infiltrate a deadly organized crime family, it doesn't exactly help if you're on the cover of Us Weekly.
If you want to be a famous FBI Special Agent, your best bet is to play one on TV. There are dozens of TV shows and dozens more films involving the Bureau in some way, sometimes as the very good guys or other times the really not great guys. Of course, you can't be an actor and an Agent at the same time, so we leave that choice to you.