This is a Falcon 9 rocket pen that I designed in Blender. It uses a BIC cartridge, and the cargo fairing is the cap. 

Due to the small contact surface, I suggest printing this slowly, especially the first layer. You can speed up after a few layers, but reduce speed again halfway through. 

Due to the shape of the model, you can consider it a bed adhesion test as well!

Depending on your printer's accuracy, you might need to scale the cap by +/-0.1mm. The original scale was good enough in my test print. 

Hope you enjoy!

Happy printing!