What is a useful 3D printed thing?

One of the goals of this blog is getting away from this:

 "Oh let me 3D scan your face and print a 3cm bust - yay 3D printing is so innovative!" 

But is it really useful? and does it justify investing in a printer yourself? Maybe something in the middle between the really gimmicky stuff and a custom solution requiring experts and hundreds of dollars.

Last year when was trying to find a good way to place the furniture in my room I could have used something like this.



The idea:

This is how imagine a simple symmetrical bracket with the ability to cross brace. One could you simple of the shelf wood beams (green) which are cut to the desired length and fixated with a screw or a wedge.
Depending on how much time one would want to spend designing one specialized piece of furniture you could either make custom brackets for certain wood beam (two by fours) and the place where the brackets sits.
As you can see in the picture not all sides need openings for 8 sides. Although I probably will design the 2nd version of this as a cube, which has 8 straight openings and also 8 openings for cross braces at a 45° angle.