H. Prologiot is a REALLY SIMPLE game made in (as you may have guessed) Prolog. Prolog is not your usually first choice when making a game, but it has some nice features I tried to exploit when it comes to game design. Mainly the fact that it actually is able to conduct deduction on its own. Therefore, a murder solving game.
You can download the Prolog source. I ran it using SWIPL. Note that it does not actually list who the murderer is - the system itself deduces the information on the run. In case you get more interested in games and Prolog, I can recommend Amzi.