- Luke: I don't believe it. Yoda: That, is why you fail. (The whole essence of the Force, if you ask me)
- Darth Vader: I am your father. Luke: No! That's not true! That's IMPOSSIBLE!
- Leia: I love you. Han: I know.
- Emperor: Strike me down with all of your hatred and your journey to the dark side will be complete!
- Luke taking Vader's mask off.
I also think that the binary sunset, the opening Star Destroyer sequence, and the Han/Greedo sequence (before it was meddled with) were up there.
Ask me about the music, and you'll get a whole 'nother story...