The etiquette of bribery, from a guy who works in personal security. Some other interesting posts there; like corrections officer Rory Miller, whose book on violence I mentioned a while back, the blog's author works in the kind of job where confrontation is a regular occurrence. While he very often carries firearms on the job, he recommends some other items as being extraordinarily useful as defensive tools, most notably the ASP collapsible baton, which the author describes as being very useful when a threat may not be big enough to go to a gun, but is something you need more than bare hands for. Also, they're useful for travelers:
Traveling into unfriendly places that say no guns and have a couple of security "conscious" buddies going along or you just like packing spares of everything? Pack two or three of the 16 or 21 (ooor 26 inch) models together wrap them with rubber bands and pack them with the camera equipment and gosh darn it if they just don't look like a tripod.
Or so I've heard.