i dont know if this is exactly in or exactly out of the HN wheelhouse, but: my keychain. it's a small hoop of plastic-coated braided strand cable with two threaded ends that screw together.
the plastic coating hasn't ripped, torn, loosened, or discolored. none of the metal has rusted. the thread pitch is big enough to screw and unscrew quickly but small enough to not loosen on its own and has good clamping force. the threaded end for passing through keys is small enough for all my fobs and keys. its tough and strong but pleasant to handle. no part of it is worse for wear even though i fidget with it and have changed keys multiple times. it also currently has like 11 keys and a large fob on it. ive had it for ~5 years and I'm fairly certain it's the most reliable thing i own. it's easy to use and easy to understand and it always does its job.
the plastic coating hasn't ripped, torn, loosened, or discolored. none of the metal has rusted. the thread pitch is big enough to screw and unscrew quickly but small enough to not loosen on its own and has good clamping force. the threaded end for passing through keys is small enough for all my fobs and keys. its tough and strong but pleasant to handle. no part of it is worse for wear even though i fidget with it and have changed keys multiple times. it also currently has like 11 keys and a large fob on it. ive had it for ~5 years and I'm fairly certain it's the most reliable thing i own. it's easy to use and easy to understand and it always does its job.
and to top it all off, it was like 70 cents.
it's a god damn marvel.
looks like this, although mine is smaller:
https://i.ebayimg.com/images/i/281726615218-0-1/s-l1000.jpg