Your bag of tricks is what helps you get things done quickly/safely/professionally/etc... The more tools you have in your bag, the more you can do with your situation. These little clamps are one of the great little tools.
All metal, save for the rubber grips. I actually trimmed the grips back because i found they smushed when clamping to flat surfaces. It feels absolutely solid.
You get 1/4" and 3/8" taps to screw into. I use male to male thread adapters to connect things such as ballheads/stud adapters. Or just screw in a friction arm.
Pretty darn infinite. I've clamped lights, cameras, audio, and other nicknacks to random places. This is where creativity comes in, so look around and see what you can come up with. A word of caution: Even with the little lever, you can clamp down pretty darn tight, so be careful not to damage softer surfaces such as wood.
Some use samples...