The most useful print I've designed - but also a simple one that took me five minutes in Blender.

This is a triangular prop with notches randomly placed on each side. The uneven sides & notches let you prop up a laptop, smartphone, tablet w/ keyboard - whatever you like. I've used it to fix a seat on a stationary bike and to prop up an iPad Pro w/ keyboard so it's at a more readable angle.

My wedges are printed on the fastest setting possible (low infill, low resolution) and they still hold up. More infill needed if you need more strength. I scale/resize like mad within the slicer itself rather than editing within Blender.. it's simple enough.