I relish tools that are as low-key as possible. That would be a reason, for instance, that I carry a folder daily instead of a fb. (There are legal issues as well, but legality aside, the folder is less likely to attract unwelcome attention.) There are obvious combat-effective tools such as Cross pens and metal mini-flashlights, but I am always eager to find new ideas for things that may serve to pull my bacon out of the fire, should I fall in.
Most especially, I am interested in things that can be regularly carried on my person, and that arguably serve other purposes. A well-made necktie has applications, and I am sure it is only a matter of time until Kevlar or Spectralight
versions are available. I have seen a variety of necklaces and chains that appeared sturdy enough for hard use, and I know ornamental and functional jewelry of this type would be easy to have custom-made. Other suggestions?