Well, the Wall Hooks contest is here, and I figured I might as well enter with my tried and tested DIN rail clip. These hooks aren't necessarily the strongest, and they won't be winning any beauty contests, but they do slide, and you can print as many as you want. I was able to print one in about 13min with the default 0.2mm SPEED profile.

Other designs based on the same DIN rail clip:

• RPiDIN 
• DIN Spool Holder