jleader asks me "Why a pin from a fire extinguisher?"

Well, I found it handy for a while as a hard thing to poke and
prod with, but small enough to fit in my pocket. Many years
ago -- to tie into another bb subject -- I used to keep a
model rocket engine clip in my wallet for similar reasons.

Off hand I can think of two things I did with the pin.

 1) Put the chain back on the sprocket of my bike without
    getting my fingers greasy.

 2) Insert it into a hole in a metal panel and use as a
    pry bar to pull the panel out.

After the panel was out I rewired some buttons to make it
easier to get to the basement of that building, but that's
a different story.