I like the idea of a discussion thread in which each post must contain a non-trivial word that occurs in the previous post, or at least a word that is a member of the same word family. An example (unintentional?) is >>264.265.266
Of course, such a thread wouldn't serve much of a purpose since there already exists a [Contentless] thread such as this one, already full of peak discussion. But I thought the idea was novel.