Grim Fandango: http://en.wikipedia.org/wiki/Grim_Fandango

Another Tim Schaefer masterpiece, the setting alone (The Mexican Land of the Dead) should be unusual enough to get you interested. On top of all of the freak and charm, there’s a fantastic game to be played, and an incredible story to be found. Sadly, you might need an emulator or something to play this one, it isn’t compliant with Windows XP or Vista.

Also, you should check out Planescape: Torment. Even if you don’t like D&D, you’ll probably love this. It’s as much of a great book as it is a great game. Plus, it’s extremely weird. Did I mention that you fight hordes of wizard rats, your best friend is a witty floating head, and you have to kill yourself numerous times to advance the plot?