Don’t know if you’ve seen this, but its a very cool student-made computer game whose premise is awesomely original.  Devil’s Tuning Fork is a first-person game where you have no “vision”.  The only way you can see is if you sound your tuning fork, and then you can “see” the sound waves as they bounce back to you.  Echo-location like a bat.  Very cool, and very impressive for a student project.

Did I mention that it’s free? (sadly only for Windows)