Hidden weapons are not the same as invisible, or improvised, weapons.
Rather, they are specifically intended to be implemented as weapons, and are designed so as to provide for maximum concealment upon one’s person.
Being designed specifically as weapons, they tend to be far more damaging than improvised weapons, which were originally intended for much different purposes. Because of their nature, hidden weapons are often prohibited by law. Depending on one’s jurisdiction, as well as the type of weapon in question, punishment can range from confiscation to years of imprisonment. Be sure to research the laws regarding weapon possession in your area before considering procurement of any exotic weaponry.
Some of these weapons are favored by gang members, ex–convicts, and professional criminals. These people are typically substance abusing repetitive felons who will not be deterred from obtaining a weapon they want simply because it has been prohibited. If your occupation, environment, or lifestyle tends to bring you into contact with such people, you run a high risk of being attacked with a weapon in the event of a violent confrontation. This section will briefly discuss how such weapons are used, where on the person they are typically concealed, and take notice of any significant weaknesses a weapon might have.
A few of the weapons listed are extremely nasty and highly illegal. Such weapons are typically the tools of assassins (whether criminal, terrorist or officially sanctioned) and would never be used by a true warrior. However, many freakish deviates fancy themselves "ninja commandos" and could conceivably procure or manufacture such devices to carry upon their persons. If you become involved in an altercation with such an individual, it is good to know what you might be up against. Exotic weaponry has long been a subject of fascination for many who walk the warrior path. In addition to being informative, this section is meant to be entertaining as well.
A partial listing of common hidden weapons follows. For purposes of brevity, this section is far from complete, as the various types of hidden weapon number in the hundreds. Many hidden weapons had only limited production or were handmade prototypes, thus are difficult to acquire. Most of the weapons listed here are currently available. Mundane weapons (such as lock-blades, hunting knives, and handguns) have been excluded from this section, as their inclusion would’ve taken up a lot of room telling you stuff that you probably already know.
This is one comprehensive guide to concealable weapons.