All my favorites have been said, but this is one of the silliest exchanges in the whole OT...
Vader: "He will come to me?"
Palp: "Yes, he will come to you and then you will bring him to me."
Cracks me up everytime.
Also, this reminds me of my favorite Star Wars joke...
Obi Wan: "I would watch out for you friend Palpatine."
Rifftrax: "Yeah, and your pal Friendpatine."
