He is not a gun.
Printed this on an Ultimaker 2, it came out very nicely. There is more iron giant coming, I'm in the process of modifying the torso for 3D printing.
Most of the parts print fine without any support on a flat surface, except the jaw. I printed this straight upwards as it sits on the model, then removed support. I then glued everything together with super glue.
The colours are a guideline. I used glow in the dark filament for the eyes, but you can use yellow or white or something similar. The silver parts can be grey if you don't have it, also.
I have also uploaded the head as a single file if that's easier.
In the pictures, I am holding the 1.5x scale version which prints a little bit nicer.