The US Navy is looking into adding 3D printers to several of their ships. The army has been utilizing 3D printing for a few years already, as a way to manufacture parts on short notice, both in and out of combat zones.
http://3dprint.com/2161/united-state...rinters-ships/

The Navy is still trying to figure out how to compensate for the movement that ships have, and the possible effects it will have on the printing process. They are looking into several uses for the printers, including medical uses. In the future they may be able to print out UAV's on short notice, which would be capable of jamming enemy's radar units. Interesting stuff for sure!