My favourite type of question has always been “is there anything that would ever convince you that the WTS wasn’t the truth?”
Really loved this point. I was with a pompous pioneer sister in field service not long ago, when I was starting to wake up to TTATT. It was her turn at the door and this householder really knew his stuff on evolution - he was shooting down the sister's classicly flawed arguments so easily - I didn't attempt to help her! It came down to the question you mentioned, but he turned it back on her. I was actually quite shocked when she said she "knew" she had "the truth" and nothing could convince her otherwise. He then called the sister on her hypocrisy: "how can you knock on my door asking me to have an open mind when you don't have one yourself?" The sister was very sheepish and the conversation then ended pretty quickly.
It was quite a shame actually as I would love to have asked him a bit more about his thoughts on evolution as he was a really interesting guy to speak to.