What can you actually use your 3D printer for? That question really becomes what do you want to use your 3D printer for?
I print parts for my RC projects, though that probably falls into the toys category of things that are 3D printed.
Two nights ago I printed a holder for my T6 thru T10 Torx drivers. No pictures, but it actually did happen.
I liked the way design worked out, so last night I started work a similar version to hold the interchangeable bits for my hex driver set. There's 6 bits in the set with the un-used bits storing in the handle of the driver; 1.5mm thru 3.0mm Allen bits, a straight screw-driver bit and about a #00 Phillip's bit. It's a hassle every time I want to change the bit to take the handle apart to get to the bit, especially finding the correct bit.
The printed items are rather light so I've been adding 1/2-13 nuts that I press into the base for weight. They sell these nuts and bolts by the pound at a nearby farm supply store for a ridiculously low price. They are just a couple of dollars per pound for the grade 5 stuff, and a one pound bag of nuts will probably last me for years.
I have an adjustable desk light, the parallelogram type, that I've had for close to 20 years. One of the plastic brackets broke so the light became junk. It was a Sunday afternoon's work to draw the bracket in 3D CAD and print replacement brackets, that was about a year ago and the light is still in service.
If you've got your printer properly tuned you can turn out parts dimensionally accurate to at least 0.1mm. My parts are good to about +/- 0.02mm, and if I worked at it I could probably get closer. (But that close enough for me right now.)
My hands have a tremor, makes it hard to crimp itty-bitty wires and terminals together and impossible to solder electronics. For a year or so I have been working on 3D printing jigs that will help me to do this. They are just about usable, and I've got a bunch of printed parts sitting on my desk waiting for me to take that project off the back-burner and get back to work on it again.
It's more of a matter of - 'What do you want to print with your 3D printer?'
Don