This is neat, they gent made a hot-end for a 3-D printer out of a cheap glue gun. Hot-ends are one of the most expensive bits (well for hobby homemade stuff) for the 3-D printers I have been tinkering in. This is an interesting alternative.
http://www.instructables.com/id/Hot-Glue-Gun-Extruder-for-Your-CNC-Machine-or-3D-P/