Any time I encounter a "compliment" that could be either a true compliment, a tease, a put-down, or whatever.. I give a relaxed "Well that's very kind of you to say," and then I change the subject.
It's just kind of a nothing reply, but it's unassailable, doesn't make you sound like a douche or a dork, and prevents you from standing there dumbfounded.
If you can come up with a witty reply (none of the above posts offered one, no offense), then go with that. But I think mine is a good backup if you can't.
If the person then replies, "I was just kidding," or "I was being sarcastic," you say, "Oh, I see," and then again change the subject.
