There are some fighters like Georges "Rush" St. Pierre whose nicknames don't really define them. Then there are fighters like BJ "The Prodigy" Penn or Chuck "The Iceman" Liddell whose names perfectly suit them.
Which nicknames would you say are the most accurate?
I'd go with...
Anthony "Showtime" Pettis - puts on a show in his fights
Jason "Mayhem" Miller - can't think of a word that better describes him than that
Anderson "The Spider" Silva - definitely uses every limb to attack