I found another unusual game that is a must-play:

Facade
http://www.interactivestory.net/

This game is an incredible leap forward in artificial intelligence. It is an interactive one-act play. You are invited over for an evening with Grace and Trip, a couple whose marriage is on very thin ice. They try to be good hosts, but their hatred for each other makes it hard to stay civil, even when guests are over. As you walk around their apartment, you can say anything you want to them. You just type it in with your keyboard and they respond. You can try to help them. You can take sides in their arguments. Fight with them. Flirt with one and break them apart. Whatever. Many different outcomes are possible, so it pays to play this game multiple times with a different agenda for each playthrough. The AI doesn’t always work, but is often successful and the potential this game has is huge.

After you have played the game, you may also be interested in this:
http://www.cc.gatech.edu/arfacade/video.html

One of the designers along with a small team of other people created an augmented reality version of the game. We are one step closer to the holodeck.