Maybe something that tests "certainty faking"? I really don't know how to construct it, per se, may use a FACS test to see how much a person is trying to convey that they're very certain of something when they aren't. That would just be conscious faking, of course; you'd still need something to assess when someone is expressing their feeling of certainty vs. the data. Maybe something like Texas Hold 'Em, except with bets being placed on how accurate the probabilities are (e.g. randomized variations of situations like the cancer scenario at EY's Bayes page).?

Sorry if I'm not articulating this well, hopefully it's good enough to live up to the stupid idea criteria, if not the good idea. Oh, and I didn't read any of the comments, so I don't know if this has been suggested.