This question falls under the heading of what has come to be known at MO as a 'fishing expedition', that is:
A question whose sole purpose seems to be to collect mathematical ephemera, motivated by nothing more than intrigue as to what the querrant might find.
They are in general poorly motivated, but tend to provide great answers as some of the high rep users pull out exotic and unheard of examples. As such they may indeed be useful for a casual reader, potentially the sort of reader that we might hope to frequent math.se, but perhaps these sorts of questions are simply too messy and unfocussed (and perhaps set dangerous precedents)...
What do we think?