Noedit: Nexus, not Rykuta. What's he doing with that avatar?
I put a monocle on it. Rykuta said it was fine.
And the other two solutions to my puzzle were:
Ask them if they would answer this question with "no," causing the honest one's head to explode.
Ask them if they would answer this question with "yes," causing the lying one's head to explode.