A classroom activity to which my teaching returns is the use of riddles as practice for both proofreading and critical thinking, something I discuss here. I have not tended to offer them as frequently to students at OSU as I have at other institutions, but their benefit is not diminished; they still do well to offer directed practice in the ideas underlying the university mission to get students to think about the details with which they are surrounded.
At this point, there is not much more to say about the riddles than I have already posted to my blog. If and when more comes up, then this place and the linked blog will update. Until then, more thinking is recommended.