I just did a 20-questions with it, and was surprised by how bad gpt4 did. Then for fun, I turned it around and had me be the guesser. It's weird and surreal to play 20-questions when you know that the clue-giver doesn't have an answer in their mind (or more literally, there isn't a single answer in any stateful form while you play), but is instead just eventually saying "yes that's what I was thinking of" when it's statistically appropriate.