My favorite single effect in all the movies would have to be in RotJ right after Admiral Ackbar says "It's a trap!" and Lando says "Fighters coming in" where hundreds of TIE fighters attack them with Star Destroyers in the background. Even with the compositing issues (a few TIE fighters appearing out of thin air) which were unavoidable at the time, seeing that on the big screen as a kid just blew me away. And the RoTJ battle is still the best space battle on film to this day, IMO.
As far as recurring effects throughout the films, the jump into hyperspace and exit from it where all the ships rapidly come toward you before slowing to a crawl was always awesome.
Best sound effect would be the lightsabers activating, being swung around, or hitting each other. It's not accidental that Hayden Christiansen and Ewan MacGregor couldn't help making the sound effect when they were swinging their practice swords during filming. That comes from a childhood spent doing that with every stick or plastic bat you could find.

As far as recurring effects throughout the films, the jump into hyperspace and exit from it where all the ships rapidly come toward you before slowing to a crawl was always awesome.


Best sound effect would be the lightsabers activating, being swung around, or hitting each other. It's not accidental that Hayden Christiansen and Ewan MacGregor couldn't help making the sound effect when they were swinging their practice swords during filming. That comes from a childhood spent doing that with every stick or plastic bat you could find.