trick question
tricky question

He'd just asked his own trick question, and gotten the right answer.

If that sounds like a trick question, that's because it is.

Here's a trick question: who's produced the most books in the past 30 years?

There's no sense in my trying to ask you a lot of trick questions.

A trick question is, how long will you be here?

At first, you might think this is a trick question.

That was, of course, supposed to be a trick question.

He had thrown her a trick question, but she was ready for it.

It's a trick question for the time being, because the answer seems to be Montreal.

The old man pulls this trick question on anyone who comes within range.