I wanted an oxygen wrench slim enough to fit in an empty shears pocket on my uniform pants, and long enough to leave a decent bit of the handle poking out to grab. None of the others I saw did both, and this also served as a good way to finally learn FreeCAD, so I made my own. I also skeletonized the handle to save material when printing it solid.

(Added updated model with a resized slot for the oxygen valve stem to fit less tightly for ease of use)