RoccondilRinon said:
I always thought he shouted "NEVER!"
So did I.
ie.:
Vader: Give yourself to the Dark Side. It is the only way you can save your friends. Yes, your thoughts betray you. Your feelings for them are strong. Especially for... sister. So, you have a twin sister. Obi-Wan was wise to hide her from me. Now his failure is complete. If you will not turn to the dark side, then perhaps she will.
Luke: NEVER!