My understanding is that many easily-concealed weapons are illegal to use for self-defense in many if not most states. For example, knuckle-dusters are illegal to use in self-defense in most if not all of the country. What I do not understand is how the courts tend to define weapons. Is there a legal difference between the following two scenarios?
A young woman leaves her martial arts practice, carrying a fighting stick which she bought online specifically for that martial art. She is attacked in the parking lot and uses the stick in self defense.
A young man is out running when someone jumps him from behind a bush. He manages to grab a heavy stick which is on the ground nearby, likely broken off a nearby tree in a recent storm. He uses that stick to fight off his assailant.
I can imagine similar analogues for other weapons. For example, knuckledusters:
A mechanic buys a pair of knuckledusters and carries them in his trendy fanny pack every day to and from work. One day he is attacked by a gang-member. He defends himself with his knuckledusters, and seriously injures his assailant.
A locksmith is walking to work when he is attacked by a gang-member. He happens to have a bunch of keys in his hand. He slips his index finger through the key-ring, turning the keys effectively into a spiked knuckleduster, and uses it as a weapon in self defense, seriously injuring his assailant.
I hope my point makes sense. While these scenarios may seem far-fetched, I imagine that people probably frequently use whatever they happen to have on hand as a weapon when attacked, if they resist at all. So in general, I'd like to know how the courts in the US tend to treat those sorts of situations, and where the line is drawn between weapons and tools or objects which coincidentally happen to be useful as weapons.
Examples of items which could coincidentally be useful as weapons could include key-rings, heavy metal flashlights, metal "tactical" pens, certain EDC tools such as this, umbrellas, heavy Stanley mugs, etc. Their real-world weapon analogues, respectively, could be knuckle-dusters, metal whap-sticks, metal spikes, knuckledusters again, fighting sticks, and clubs.