WHY? 
Picture frame hanger. Purposefully designed for our large 6 foot (1.8m) picture with a slotted frame. Thought I would share because we got it from a major retailer and other people may have the same frame. 
 

WHAT?
There are two versions (installation pictures are of stud version):

Stud - This version is for the center screw going into a stud. Screw in hanger, level, use drywall pins to set - I hammered mine in after using a nail to make a starting hole.
 

Anchor - This version is for using drywall anchor screws. Level, mark holes, drive anchors, screw hanger onto anchors.
 

Print Details

Hangers
material: PETG for the toughness but PLA+ would probably work in a temperature controlled home.
infill: 15%
support: Yes

Drywall Pins
material:  PETG
infill:  100%
support: No