I guess we shouldn't be too surprised anymore at what can be done with 3D-printing machines. After all, companies like Local Motors are constructing whole cars using the technology, but it's still always interesting to see what people are coming up.
For example, it's hard not to notice when someone builds a working 3D-printed model of a LS3 V8 engine from a Chevrolet Camaro. The video below shows the model being assembled like a real engine, and "running" on an engine stand. With the exception of the bearings and fasteners, all parts were 3D-printed.
Parts for the undeniably cool piece were modeled from CAD files found on the internet, as well as pictures and diagrams from repair manuals.