THE RULER!!!! I have many of these items, but the ruler is what I use the most! I typically use it as a straight edge, but I also use it as a way to point out small features or small parts on items I show to customers in my "retail" job. Having a legit hard use ruler isn't an item I ever thought I'd add to my pockets, but now I can't part with it.
I use mine as a defensive tool. Make the paracord longer and swing that dude around. 😄 I buy most of mine from a guy on the east coast and he makes one you could darn near use as a baton.
