Useful

I needed a pair of tweezers to pull extra filament from the tip of my extruder. This one is interesting since I wouldn't need it if I didn't have a 3D Printer so it will save me $5, but I wouldn't have needed to spend the $5 to begin with if I didn't have the 3D printer. But I'm going to count it anyway.

Certain times a day the sun hits our garage door sensor and it tricks it into thinking there is an object in the way. I could have replaced the sensor which probably would have fixed the problem, but the sensor works. It just gives false positives at certain times on a sunny day.  It's pretty rare, but when it happens, and you are in a hurry, it's a real pain. So this is a solution to the problem, that saves roughly $60-$70. 

Fix broken door bell on back porch. I'll have to design it since there isn't a compatible one online.

Not very strong, but a good solution for keeping a gate latched. If you are going to a hardware store for something else you would be better off buying one than building it. But I like finding any reason to use my 3D printer, so a quick $5 - $10 savings.

You can never have enough little storage systems for small parts, screws, etc.... This is customizable to match your specific needs.

These are nice for storing any item you'd like to keep seperate from other similar items.  Nuts and bolts are the best example since there are so many different sizes you don't want to have to sort through to find the right size. These usually cost around $5 a piece. You would want quite a few of these. To organize my nuts and bolts, I'm guessing I'll need around 10