I found this on Google this morning. This guy created a "3D printing pen" using a hot glue gun. OK, maybe it's not a pen, but it uses the same idea. However, his "printer" works better because you can control the speed of the extrusion, whereas on pens like the 3Doodler you only have 1 speed.



While this was a joke. It supports "glue gun material" LOL. Couldn't this easily be modified to extrude filament through a smaller nozzle?