Re: @Paul Crawford re: guns.
The problem I have with your argument is that in all the examples you give a tool is being mis-used to do someone harm, and also it needs a much closer and physical approach to achieve that harm, which then entails the risk of losing a physical fight.
A Gun is the only object in your list that is expressly designed to do another person harm whilst still staying at a safe distance yourself, thus making it a lot easier to harm someone else without entailing any personal risk.
If someone had to use one of the alternative methods you list, then a lot of potentials killers would think twice and back off.
That's the real problem with guns, it makes it too easy for a coward to intimidate or kill someone that they won't take on face to face.