"Yeah Right" sticker
3" high vinyl sticker. It depict a skeptical-looking (or maybe just inexpressive) fellow saying "Yeah right."
There's a story I like about a professor telling the class "there are many examples of a double negative being used tto express a positive, but no examples of the opposite," and voice from the back of the class pipes up "Yeah, right." I don't think it ever happened but I like the story just the same.
So buy some stickers.