Well, the things that I tend to do most often is make my own tools for fairly specific tasks. One of my greatest eureka moments was when I realised that I can 3D print my own tool to open a watch case. It took a few iterations (plastic after all is weak), but I finally hit on something that's reliable enough, and it won't scratch the watch case. This was all because I took it in some years ago for a battery change, and the person kind of made a mess of trying to open it, they bent a strap pin, put tears in the leather strap, and scratched the case back. Fortunately it was my cheap daily watch, but still, I got paranoid after that, and had no intention of going to that person again. Now, I save a few dollars by buying my own batteries, and they're good brand ones too, and use a plastic tool to open the watch. No chance of marking it.
The point isn't so much that 3D printing is awesome, but it's really great when you realise that with this tool (3D printer that is) I can do things which I previously would never do. I'd never consider making a tool before unless it could be made with sheet metal and a hammer and file, and in some ways, the tool I made is better than one I could buy.