Episode VI was originally called 'Revenge of the Jedi' instead of 'Return of the Jedi'. Here's the trailer =)

WikiPedia: The film was originally titled Revenge of the Jedi, and the original teaser trailer for the film carried this moniker. A released teaser poster created by Bill Pate containing the dismissed title has since become a rare collector's item. Of notice are the lightsaber colors on the teaser poster shown: Luke is seen wielding a red lightsaber while Vader wields a blue one. However, a few weeks before the film's premiere, Lucas changed the title, saying "revenge" could not be used, as it is not a Jedi concept. The 2005 prequel trilogy film Star Wars Episode III: Revenge of the Sith later alluded to the dismissed title of Revenge of the Jedi.