Twenty Questions is a game with very simple rules. One person thinks of something and through a series of up to 20 yes or no questions, the guesser must determine what it is. Over time, players learn to hone in on the objects by asking general questions at first such as, "Is it an animal?" or "Is it bigger than a breadbox?" Eventually, the game depends upon the obscureness of the object chosen and the skill of the interviewer.
It was predictable then that eventually someone would write a program that would play the interviewer. In comes 20Q, a round toy about the size of a yo-yo. A small LED scrolling text window asks the question and you scroll to the answer. Since no AI has ever exceeded the full capabilities of a human mind, the toy does establish a few guidelines and takes a few shortcuts, like asking if it's animal, vegetable or mineral with the first question. Follow-up questions can be answered yes, no, unknown, irrelvant, probably, doubtful, sometimes, usually, rarely and give-up.
We were amazed that this little device actually could get it after about 15 questions. You can also play it online for free at www.20q.net.