One could mention Spock's claim that he was the second
officer of the ship in "The Enemy Within", or Picard's introduction in "The Battle" of Data as his second in command despite Riker being his First Officer.
Also, I trust people are refraining from mentioning Peter David's famous splitting of the 1st Officer and XO jobs between two characters in his New Frontier
graphic-free graphic novels for the sake of decency rather than incompleteness...
Whatever else be said, "Executive Officer" isn't a popular title in Starfleet. Either the superiors and inferiors of Executive Officers hate the term and use any available alternative whenever they can, or then this type of officer isn't part of the usual complement of a starship.