I know this sounds boring, but I would definitely use a 3D printer to make household repairs. Replacement parts are often sold at a ridiculous markup and I would love to print out my own. Might take some trial and error / frustration but it would be better than paying a company $20 for a $0.20 piece of plastic.
I've been able to print toys with mine. I was thinking I could print parts/gears for robots but so far the stuff isn't dense/strong enough. I'm sure I'm doing something wrong, going to try 3mm filment and see how that works.
I long for the day I can print car parts and relatively heavy duty mechanical components. For people like me who are decent with a wrench and like to tinker that would be a god send. Not to mention it would make owning a classic so much more practical. Parts get really expensive for older rarer cars.
That would be awesome. I'd print off a turbocharger, exhaust manifold, high spec pistons and conrods. I hate having to pay the ridiculous prices for custom made manifolds!
1) Game pieces and parts
2) "upgrades" for store bought stuff.
3) experimental stuff - different pen shapes for example.
Hardware like nails and screws that you only need one of, but have to buy in packs of 100.