Has anybody guessed what Lucas' favorite word is? It's "no". Lets take a look:

Episode I: Gui-Gon dies: Obi-Wan screams "Noooooo!"
Episode II: Anakin cries out "No!" as he has the nightmare about Shmi.
Episode III: Palpatine says "No. Noooo!" before shocking Mace Windu
Episode III: Vader learns that Padme is dead and screams "Noooooo!"
Episode IV: Obi-Wan dies and Lukes cries out "No!"
Episode V: Luke cries out "No. No. That's not true." and "Nooo! Noo! No!"
Episode VI: A Gunk Droid gets tortured and screams "No!"
Episode VI: Vader cries "No. Nooooo!" as Luke almost dies in the (butchered) Blu-ray version.