ANH Yoda v. ANH Palpatine
In ROTS, Master Yoda and Emperor Palpatine faced off in the Senate Rotunda. The battle was a stalemate, according to the official website, with ultimately both sides forced to regroup. Many feel that Yoda was superior to Palpatine, and that the Dark Lord merely had luck and a terrain advantage. Others, like myself, believe the battle was designed - for all intents and purposes - to be an equal showdown between the most powerful light side practitioner (Yoda) and the most powerful dark side practitioner (Palpatine).
Flash foward twenty odd years to the time of A New Hope. The Empire reigns tyrannically over the galaxy. The Emperor's Starfleet and Army police the galaxy, and most signs of rebellion are crushed between the perpetual boots of the Stormtroopers. On Dagobah, Yoda has lost hope in the belief that the prophecy will be fulfilled. He is getting too old, and he will soon become one with the Force. So, Yoda decides to take one final gamble on putting down Emperor Palpatine, and allows himself to be captured by the Imperial Fleet.
Yoda is taken to Coruscant, where he is placed in Palpatine's throne room, before the cackling Sith Lord. Calling on the Force, however, Yoda mimics a move that he used twenty years before, and disables the Imperial Guards with a mighty Force push. Reaching into the folds of his cloak, Yoda retrieves his dusty lightsaber and ignites the emerald blade. The Emperor rises from his throne and glares down at the Jedi Master. Reaching a gnarled hand into his sleeve, he brandishes his sleek saber and activates the crimson blade.
Yoda, deep within the heart of Imperial City, realize that he will die, despite the outcome of this duel. If Palpatine does not slay him, Vader or the Stormtroopers will. With this knowledge, the Jedi Master takes his final stand against the last Dark Lord of the Sith.
Both combatants rush forward, with the movements of beings who haven't touched their sabers in years. Crimson and emerald clash together in a mixture of sparks.
The battle is on.