I use an old biner my brother was going to retire becuase of some corrosion. MIght not hold him, and I'm not even remotely stupid enough to try to climb with it, but it holds my keys just fine.

To save wear on my jeans, I used to put a loop of gutted paracord around my belt. But I never noticed it made a difference with good jeans. With slacks I might to that, but I don't wear those very often.