Carabiner Multi Tool

~$6

The carabiner form factor is underrated for stage work. This one clips to a belt loop, bag strap, or road case handle and gives you a bottle opener, small blade, file, and screwdriver without adding bulk to your pockets. It's especially handy during changeovers when you want quick access to basic tools without digging through a bag. Clip it, forget it, use it constantly.