Summary

... to hang stuff on sheetrock walls.

Instructions

Sheetrock / wallboard / plasterboard / drywall / hanger / anchor.

Prints differ from injection molding in many ways. They have distinct directional weakness and layers are split easily. Prints also lack flexibility. Many tried and true molded-part designs don't translate well to 3D prints.

This 2-piece anchor attempts to take advantage of a print's strengths while minimizing weaknesses. The tapered core expands the shell. The screw provides longitudinal strength to the assembly.
Coarse (0.30 mm Z) layering seems to be an advantage. The bumpiness in adjacent surfaces helps lock the parts together.

The anchor was tested in 5/8" rock but should be OK with regular household 1/2 inch... It might be best to try it in a clothes closet first so nobody notices the damage.

Drill a 5/16 inch (8 mm) hole. Push the shell into the hole (probably need a hammer). Align and insert the core (gonna need the hammer again). Then drive in the screw.
Standard 1.25" "fine" thread drywall screws seem best.They are thin, hardened and strong.

Photo shows a 15 lb (7 kilo) dumbbell hanging from a wire. I gently let that go fearing it would pull out but the anchor can actually support more weight. I'd never hang a heavy weight except to test it and was not too interested in exactly how much more, so quit while I was ahead.

Removal: First remove the core with a thin, stiff blade so the shell contracts and it can be removed. [EDIT My mistake. The core's head just breaks off if you try to remove it like that. Instead, back out the screw part of the way, protect the wall and use a claw hammer to remove screw + core. Then the shell can be removed.]

Printing 6 units (12 pieces) required ~40 minutes and 10 grams ABS using Afinia defaults: 0.30 Z, medium speed and fill with a raft.

Printing several at one time did eliminate the need for fan-cooling.
Carefully separate rafts to preserve the little shoulders on the parts.

Picture hanger / drywall anchor