The coolest use of a 3d printer is making organs. Google "3d printer kidney". THAT's some cool shit.
Wow that's amazing I googled it - and it's unreal. I had no idea they could do this!
Its one of those TED talks (a little long but worth it I thought).
Yeah, pretty cool, but as the video says it's still a few years away. However, I found an article yesterday that brings it a little closer: