Is your listless collection of pens and pencils moldering away in an old, chipped "World's Greatest Dad" mug? Liven up your scribe-ware with a ballistic array of pen/pencil launch tubes! Just flick the little thwacker at the bottom of the tube, and your favorite writing implement presents itself, mid-aid, ready to grab and write. Don't believe me, just watch:

Print as many as you like - they interconnect with dovetail slots in the back. I've also provided two different heights: full-stealth, where you can't see what's coming, or stubby, for those of us who can't remember what's in each silo. I've also provided left-end/right-end versions, each without one part of the dovetail, for a cleaner look. Works with pencils and most pens (Bic, Papermate, etc.).

Printing
Use PLA for the stiffest thwacker (and greatest launch altitude). Use a 0.4mm line width and a 0.2mm layer height. All parts print in the orientations provided, and without supports. This prints very easily, but make sure your first layer adheres completely. The design is tolerant of a little bit of elephant's foot, but any warping around the dovetail will cause problems. If you are having trouble printing without the corners lifting, you may need to add a brim.

Assembly
Test assemble the dovetail joint incrementally - don't try jamming it together all at once or else it might get stuck half-way if the joint is too tight. If it is, you may need to go at the dovetail surfaces with a needle file or sand paper. (Or you can always re-print with a lower extrusion multiplier.) If the joints are a little loose, you can use a drop of superglue (permanent!) or simply put a piece of tape across the bottom to keep them aligned. Some sort of non-slip tape on the bottom is nice anyway, to keep it from scooting around on your desk as you launch pencils.