Ok, well, inconspicuous to the point that you can possibly bring it in a high-security premise like where im working which any recording device isn't allowed as well. Before i forget, im also gonna learn some martial arts. Well, when facing a group, armed (like gun), or the circumstance needs you to end the fight very quick, martial arts is not always the answer. That's why im want to equip myself with some handy weapons. For instance, the gun spear, which is disguised as umbrella, if you bring it public, it totally not suspicious, and in office, you only have to keep it on your locker area. For the highly-durable, non-metal knuckle fist, you can attach to your belt and disguise it like as part of the belt. Even in the working area, you have a nice friend under ur sleeve. Well, for the taser gun/stun gun, but i already have the shock mechanism in the gun spear. For the candy explosive, only small explosion like some weak fireworks (that can damage and not cut a finger). But for the explosive, we can drop this if its case sensitive. Taser/Stun gun is only good in close quarter but what if theres quiet a distance from a gunner?
Inconspicuous weapons has to be natural items to work. A foot or so of paracord, a steel ring/keyring, or a monkeyfist works very nice. Keys always gets checked in at metal detectors and slid across. With just few minutes work you can strike fairly accurately. Adding kubatons made from ceramic, wood, or pvc is nice as well.
v3luotianyi, none of your proposals fit well into anything we do here in the United States, so we have little to no useful input for your ideas. Many of them have been seen in popular media such as spy films, but as it's always said, the only reason they work in the movies is because it's in the script.
Here in the US we use lawfully carried firearms, knives, pepper spray, and the occasional blackthorn walking stick. All legal in the jurisdictions we live in, with whatever permitting system that may exist in that political subdivision. I am fortunate to live in Arizona, so I need no permit, license, registration, or other legal impediment to carrying all the above for lawful self defense.
If you can frame questions within the above parameters, perhaps we could help, but honestly, none of the things you are proposing are anything we would have serious experience with currently.