I present my Triangular Capped Pen, designed to hold a Parker G2 type ballpoint or gel refill (not included).
The pen is made up of three printed parts: The body, the cap and the tail screw. All three parts are included in this model.
The hole down the centre of the pen's body may need to be hollowed out, due to unfused powder becoming trapped within it. This can be done with a toothpick or other narrow pointed object.