I’m not sure exactly where this originated from, but I’m quite delighted by this exam question:

State some substantive question which you thought might appear on this exam, but did not. Answer this question (correctly).

As an interview question, I’ll sometimes ask: “Tell me something interesting you’ve discovered or learned recently.” I find its goes a long way to understanding the way the candidate thinks; how they convey technical knowledge to others; and to get a flavour for how real their passion and interest is for the domain.