This is certainly one that has opened my eyes. Check it out. This is a jet engine constructed by various parts made on a 3D Printer:
http://youtu.be/6rX4xv5-NvE
Best of all the design can be downloaded here:http://www.thingiverse.com/thing:114468
http://www.3ders.org//images/jet-eng...printing-1.jpg