I just printed a Heptagonal-Finger-Ring for my wife. I like 3d printed jewelry. And I also like to work with heptagons. I dont't get that chance very often, since they don't make patterns that easy - at least not in an euclidian space that doesn't cause your mind to explode
I own a Ikea-pen holder on my desk which I like very much, but It has one very large compartment in the front, where I wanted to put my markers. Since I don't have enough markers to fill the whole compartment, I designed a small box in openscad and printed it on my makerbot - et voila! a smaller compartment for my pens.
The box is for sure not the biggest innovation in 3D desgin and I could have used cardboard boxes too, but I really like the idea using a 3D printer to personalize off the shelf furniture :-)