I wanted a way to look at the G-code start and end codes that are created by slicing packages. Slic3r won't let me write a G-code without having an STL file loaded. My solution was to design a cube with 1mm edge dimensions. This produces a G-code file of only a few kb and a few hundred lines. If you want the smallest file, make sure you turn off loops, skirt and brim so that the body of the G code only "prints" the cube.
I haven't tried printing this. I doubt it would be very exciting, but you are welcome to try.