Strictly speaking here, something that could be fully repaired by the actual tools I have without just swapping for new purchased replacement parts would probably be one of my guitars. I could essentially make every piece of them from scratch if needed except maybe the pots, caps, and truss rod. I could probably repair the truss rod but making one from scratch would be tricky. If I had an acoustic guitar, that would be an easy answer.

It might not turn out well, but I could make it playable again.

I could repair anything on my bike, and kayak. I might be able to rebuild my snes on a component level.

If you allow replacement parts, almost anything can be repaired of you are willing to spend enough on it.