Many years ago I was given a Rexel "
Staple Wizard". This brightly coloured toy, clearly designed to entice small children to stick their fingers into the mechanism and thereby learn an important life lesson, has been surprisingly useful over the years and has seen a fair amount of use.
It's been fixed before; plastic parts have cracked and failed, and I've replaced them with similar components fabricated from whatever I happened to have lying around at the time. Now I have a 3D printer, there's no reason I shouldn't be able to keep it going forever - so I wasn't too bothered when my wife mentioned it had stopped working.
I tried it with a sheet of scrap paper, and it dutifully whirred into life and ejected a staple, albeit without much enthusiasm.
Rule 1: check power supplies, and sure enough, a couple of its batteries (dated 2012!) had started to leak. No problem, just take them out, clean up the contacts and replace. Totally routine maintenance, 5 minutes' work at most.
New batteries fitted, insert another sheet of scrap paper, and:
chomp

chomp

chomp

chomp

chomp

chomp

chomp

chomp

chomp

chomp

chomp

chomp

chomp

chomp

...
It put 3 staples in the paper before I was able to pull it out, then proceeded to chew its way through the entire stack, depositing them one at a time on my desk. By the time I could get a battery out, it had eaten the lot.
Turned out to be a failed capacitor, easily spotted under close inspection as it was leaking electrolyte. Desolder, swap, reassemble and test, and now it's back to its usual self. Should be good for a few more years now at least.
A brand new one is £18 but I've grown quite attached to this one, with its variety of hand fabricated parts keeping it running. I do enjoy repairs, when they're not made unnecessarily difficult, and this device is dead easy to open up and dismantle.
What have you enjoyed fixing, that could easily have gone in the bin but for a little TLC?