A while back a friend of mine who works at a gas station brought home an entire display container of key chain carabiners. They were pretty good quality (more so than the couple I already had) So I took 35 of them to find uses for.
This is my list.
1 - My cell phone's lanyard clips into one that stays on my tengu harness, right next to the accessory gap in the waist strap that my cell phone holster is clipped into.
2 - The tail end of my throw line is tied onto one with an anchor hitch. This usually is clipped onto the tag in the bottom of my throw line cube to prevent disappearing throw lines. However, when I want to attach the tail of the throw line onto the weight, to isolate a branch or other reasons, I just clip it to the loop on the bottom of the throw weight. If I think I need extra weight to overpower the friction when isolating a branch, I clip my extra throw weight, and sometimes creative bits of extra weight right to the key chain 'biner
3 - One stays stored on the handle of my throwline cube that is used to pull my climb line up and over the branch, I just clip the eye splice right to the bottom loop of the throw weight and pull it over. 99% of the time it pulls over just fine. No problems setting the cambium saver. Even when things kinda got stuck, I tied a loop in my throw line so I could sit in it and bounced my full weight to break the rope free. The keychain carabiner was barely bent. I had to chuck it in the trash but it got the job done.
4 - When quickly flaking my throw line back into the cube I will run the line through the little carabiner like a hand held redirect, so that it doesn't rope burn my fingers.
5 - One stays clipped to my camelbak to keep the tube from getting pinched between the saddle's waist strap and my waist, causing water to flow, and me to look like I wet my harness.
6 - Another is stored on my camelbak's shoulder strap as an extra for whatever random need may arise. They make a great extra set of fingers when you just gotta hold three things for a second.
Those are the standard uses in my climbing system nowadays.
I have also used these little carabiners in place of a micro-pully in an attempt to improvise a hitch tending method. It worked, but not well.
Anyone else use these things, or have other ideas???
Carl