A lot of Joel David Hamkins best questions are things which are really elementary in statement, but quickly lead to thorny logical issues. Examples here are this question about a game involving chocolate eating or this question about Hex on an infinite board. At the same time, many of his answers to more traditional logic and set theory questions are really fantastic, helping (at least for me but I suspect for others as well) understand a lot of subtle points in set theory and model theory. I made a joke to someone a few days ago that "I'm not a logician but I read JDH's Mathoverflow answers regularly" but it really was only halfway a joke.