This is a killer gadget that will help you kill balloons. As commented on over at Topless Robot,

So some dude built a phaser. Like, a real one. From bits of a Blu-ray player, an old Playmates phaser toy, and some other stuff. I don’t think it could kill anyone, but it would certainly stun them if you shot them in the eyes with it — since they’d be painfully blinded, possibly for life.

This is a great object that will levitate objects with sound, while at the same time killing people with the obnoxiousness of said sound.

As commented on at Boing Boing:

Do you want to hear the most annoying sound in the world? What about watching the most annoying sound in the world levitate objects?

Btw, a recent Wired article discusses how acoustic levitation could be used on Mars.

Also  linked up at Boing Boing: a business card that converts into a penny launcher. So you can kill on some businessmen (well, you can least put an eye out) with this handy covert device.