I've recently become enamored with 3D printing and picked up a kit printer to assemble - it's working and seems to be dialed in pretty well now. Even used it for some photography related items:
An OEM-style hood for my Sigma 70-200/2.8. I have the older APO EX version and the hood is a tiny bit smaller than the later models. I've been on the lookout for an original hood for probably 5 years and have never seen one for sale. Someone else must have been in the same boat, because they uploaded their design to thingiverse.com. I printed one and it fits quite well - even reverses and locks on like an OEM hood! I've sanded the inside of the hood to reduce reflections, but it could still use a coat of flat black paint.
I've also been on the prowl for a Tamron palm rest, and finally got one off of eBay not too long ago. They seem to be quite rare, so I made an attempt to print my own so I don't have to worry about losing my long-sought-after original.
First attempt on the left to check sizing, second attempt on the right with some smoother curves and a couple of rounded edges to make it more comfortable. The printed ones look a lot bigger, but they're really not - I think it's a trick of perspective in the photo and that the original has all rounded corners and edges. Haven't tried using it much yet, but it seems to fit pretty well and feels about as strong as the original. Here it is mounted on a Tamron 360B, using the original's screw to attach it. I need to find a suitable replacement for that piece also...
And lastly, a little hotshoe mount that clips onto a light stand to hold a remote trigger receiver (hotshoe copied from a design uploaded to thingiverse.com and modified to add a clip that fits the diameter of my light stand - and stays in place by friction, at least with a lightweight Cowboy Studio receiver):