My favorite part is where Obi-Wan Kenobi kills General Grevious on Utapau. The chase scene with Obi-Wan on Boga and Grevious on his wheelbike rivals any car chase scene in recent times. That wheelbike was one awesome machine!
OH good grief, this question is a killer for me!!! lol I can never ever ever decide...I love each scene from EVERY movie!! But, if I really honestly do have to choose, then I pick the epic, plot-twisting battle between Anakin and Obi-Wan. Jedi Master vs. Former Jedi Apprentice; one of the most long-awaited battles since it all began. It's one of the key and ultimate turning events in the entire Star Wars saga.
Omg my favorite scene is when Anakin betrays the Jedi, almost kills poor Padme, battles in an epic Lightsaber battle, and finally turns into Darth Vader. Love, betrayal, hate, its just so much drama! xD