Imagine a weapon that creates sound that only you can hear. Science fiction? No, this is one area that has a very solid basis in reality. The Air Force has experimented with microwaves that create sounds in people's head (which they've called a possible psychological warfare tool), and American Technologies can "beam" sounds to specific targets with their patented HyperSound (and yes, I've heard/seen them demonstrate the speakers, and they are shockingly effective).
http://www.woodynorris.com/Articles/NewYorkTimesMagazine.htm