Cylon raider? A new Tron vehicle that we'll see in an upcoming director's cut? Definitive proof that we are not alone? Actually, it's none of those things, but the dead silence it produces is amazing anyway.
While some work toward an invisibility cloak, University of Illinois professor Nicholas Fang is taking steps to create a similar material, only for sound, that could, for example, make ships invisible to SONAR. To successfully do this, of course, requires we break the laws of physics. But, you know, whatever.