Not really a comeback, but still good.
Were all sitting at the table during the lunch period eating and whatever. The usual talk, joking, etc. Anyways, the annoying guy most of us don't like but he hangs out with us anyways starts going around doing this: "I think your going to go out with [insert person]". He keeps going around telling each person who he thinks they'll be with. I was done eating and getting ready to leave, so I interrupted him and said something like "I think you're going to go out with NOBODY." Then I left. His face was priceless.