no there aren't but heres a tip, If you cant beat a boss just keep fighting monsters to a certain level you want at the end of the game I had 10,000 hp points!
Well, there is one, but it's more of a glitch than a cheat. You can use it to clone any usable item, such as Chocobo's Wrath or Elixers or Phoenix Downs, but you can't clone equipment like shurikens...