Fiber One: Cardboard No, Delicious Yes.

Unlike the last two, this "We are ____, not ____" falls flat. Reason being, it doesn't stand alone. Sure, it works well with the commercial where Mrs. McCluskey from Desperate Housewives makes a crack about having to eat the box to get the fiber. But they use it on the homepage of their website, where surely noone is putting two and two together. Good Slogan No, Good Try Yes.