Weapons are only used against ourselves...

Guns.

What if all fire arms would be prohibited?
I know that quite a few arm dealers and weapon makers will be out of a job but I think that the majority of the population would not really care about that. Oh and quite a large number of people in the army would have to try and learn to do something else. (Help people instead of shooting them is something that jumps to mind).
And oh, yes, I forgot that a number of gun toting inhabitants of our planet would probably feel extremely vulnerable. But if we do ban guns entirely there is a chance that this heck of a list stops growing.
The bit that surprises me the most is when after those killings people wonder how this could have happened. Well those wondering and not understanding people are lucky right now, I can and will explain how this can happen. The thing to remember is that in all those gun killings the basic principle is the same:
You aim the gun at the target and you pull the trigger. There you go, that's how it's happening. Yes I hear you say, but how can somebody shoot that sweet 3 year old little girl/boy? Well: you aim the gun at the target (in this case a 3 year old little girl/boy) and you pull the trigger. There you go, that's how it's happening.Was that in thick black sentence not clear enough? Let me help you:
You aim the gun at the target and you pull the trigger!!! 
There you are, you should start to grasp the idea by now.
You see the thing with guns is, as long as you don't get the death penalty if you do posses a gun, these things will continue to happen. Yes, I said death penalty, I'm a simple person, my logic is simple, if you posses a gun, you are a potential killer.
What do you think guns are for? Knitting? Car repairs? Unplugging the toilet?
When weapons are available to anybody, there will always be somebody who will pull the trigger and the only reason that this person will pull the trigger is because he/she had the possibility to do so. So you have to make sure that nobody wants to have a fire arm.


Explosives. 
We don't need explosives. I know that this may sound strange to you but we honestly do not need explosives.We can live and will survive without them. Yes, more things will have to be taken care of manually and that will lead to the creation of more work, isn't that wonderful?
When I talk about explosives, I mean everything that goes boom: dynamite, torpedo's, nuclear devices, hand grenades, missiles etc. etc.
In order to make you see why I think we can live without the on-purpose-created-devices-that-go-boom-and-kill, I've done some research on events that happened with explosives. Not to prove from a scientific point what we are capable of but more to show what we are inflicting on our fellow humans.

Atomic Bombs - (info taken from wikipedia)
The result of throwing two man made bombs came down to this:
Within the first two to four months of the bombings, the acute effects killed 90,000–166,000 people in Hiroshima and 60,000–80,000 in Nagasaki, with roughly half of the deaths in each city occurring on the first day. The Hiroshima prefecture health department estimated that, of the people who died on the day of the explosion, 60% died from flash or flame burns, 30% from falling debris and 10% from other causes. During the following months, large numbers died from the effect of burns, radiation sickness, and other injuries, compounded by illness. 

On the question how many a-bombs there are in the world today, wiki-answers came up with an estimation of 70.000 nuclear bombs. Now let's keep things on the low side and lets calculate:
70.000 bombs x 60.000 people killed per bomb = 4.200.000.000 people dead.
The estimated population today is almost 7.100.000.000
Well look at that: with very little effort we can reduce the population to less than half. And mind you this would be the result of the first two to four months. Surely if we place our bombs well we can do better than that? Let's aim for oil fields, gas fields and electricity dams.
Other strategic points*that will help to cause dead and destruction are the next ones:

St Helens, USA - Surtsey, Iceland -  Ring Of Fire in the Pacific Ocean - Paricutin, Mexico - Pinatubo, Philippines - Krakatoa. Indonesia 

These places are volcano's and edges of techtonic plates. There are a few more but these are, at the moment of writing this story, the most dangerous ones. If we drop on each of these points ten nuclear bombs we may be able to start something with such disastrous results as: 

Volcanic eruptions, earth quakes, radiation, ash clouds (also radio active these clouds, it's just a bonus, sit back and appreciate it), tsunami's, complete standstill of all electric devices and most mechanical devices, destruction of all agricultural land, poisoning drinking water and killing off all sorts of animals that we could have eaten, well... 

I think we have a winner here. And the best part is: There are still 69.940 bombs left. The eventual survivors will surely appreciate this and use them well... 

Here you can see what the result is after humans were exposed to a nuclear explosion, the story, where I found these images is irrelevant (well at least it shows that man kind is still stupid) but some of the pictures may give you an idea of how civilised we really are...

* And to give you an idea of what happens to Earth when one volcano erupts, here's some info on that topic as well. It will show you that I am not exaggerating with my strategic points story.

Non atomic bombs.
Humans don't always want to kill vast amounts of people or destroy their living area's for years to come. No sometimes all they want is just kill some people, knock down a building or two and get on with their daily routine.
So different bombs are needed. And as people are beings with a very destructive nature they have developed ways of creating explosives for all sorts of occasions. I'm not going to tell you how you can make or get your hands on these bombs. If you are an enthusiast, you will have to do your own research on that one. I've made a list of devices that go boom and kill but there is also a very particular way of killing people and that  is with the so called car bombs. It's also one of the most popular ways of killing because you can make the explosion almost as big as you want and detonate whenever you want and  from where ever you want as you do not have to be there yourself. The great advantage of a car bomb is that the explosives are totally out of sight but can be brought very close to the target. I know, it's useless in the jungle or at sea because it's not easy to get a car there but it does a great job in cities and villages. Have a look at this. In 1920 they were already doing a car bombing with a result of 38 deaths. This literally must have paved the way and certainly became an inspiration for others.

Swords, knives and all sorts of weaponry like this made from metal (scissors, machetes) etc.should not be allowed to be carried on a person when this person leaves the house/home terrain. A simple detector build at every entrance/exit of every building can give a warning sign. Finding yourself in public area's with this kind of weaponry on you should result in a fine of forty percent of your income during two years or a year in prison. After all you still are a potential killer while carrying this sort of weaponry with you and there simply is no need for it.
How do you get your cutlery at home? Your cutlery  should be delivered. A special service is to be set up and deliver these kind of utensils at your home and bring them inside. All knives and cutting utensils will have a serial number and a chip so that they can be counted for and tracked when this may be necessary.

In any case: all weaponry should be prohibited except riffles to hunt.

The one and only fire arm that should be allowed, to be used by a specific, designated group of people, are rifles used by hunters. Hunters have to reside in area's where hunting can be done. Even hunters can not bring their rifles in a public area except those designated for hunting. These hunters have to be single, between 30 and 45 years old, teetotal and not wear glasses or lenses. The rifles have to be activated with the help of an eye scan. So no rifle can be fired by anybody else but the rightful user. If you don't fulfill these criteria, you can not be a hunter and therefor not use a rifle.
Every other fire arm but such a hunting rifle is only created to kill people and should result in obtaining the death penalty for possession.