We've seen people attempt invisibility cloaks for ages, mostly failing miserably, even in films. But how about hiding something with darkness. That's what researchers using carbon nanotube forests are attempting to do.
Carbon nanotubes can be grown and mounted on the surface of a material so that they're standing up perpendicular to the object they're covering. In this way, light coming in is trapped and can't escape from the forest of nanotubes, in effect, preventing you from seeing it. In reality what it does is create an absence of light where the object used to be, making it invisible.
Unfortunately you can still see it because it stands out as the only black void on the landscape -- a dark patch shaped like a tank still looks like a tank. Having said that, it'll do wonders for when we're attempting to conquer other worlds; we'll be able to black-out our spaceships, blending them into the dark void of space. The aliens won't know what hit them. [American Institute of Physics via Dvice]