This question is poorly couched. ANY weapon! Goodness, a person could use a house-brick or a horse shoe for a weapon. Knives can be obtained from kitchens. Poison can be bought or brewed. Blankets and pillow can be used to smother. Then we have hatchets, pick axes and vertually anything that can be either thought of or picked up and random. Please be specific!
If you are talking about firearms, particularly military-style weapons or even hand guns such as revolvers or sem-automatics, these should be banned totally. No one should be allowed to have them except the military and the police. And even police should be obliged to keep their firearms hidden under the uniforms and not displayed on the hip like a western gun-fighter.
Certain farmers and people on the land would need to have access to shotguns and possibly rifles. These might be needed to kill vermin or put down sick animals. But in this case an extremely rigid licencing would be needed with all sorts of provisos as to the save keeping of those weapons, e.g. lock and key, amunition kept separate and also under lock and key.
The problem in America is obviously your gun laws. "Right to bear arms." Cripes, this came into being when the newly formed government thought the British might be back, or the French or Spaniards might invade. At best, muskets were needed to fight off hostile Indians. But today the need to "bear arms" is well and truly passed.
Until the American Constitution is changed and this "right to bear arms" is rescinded, you will continue to have ten times as many shooting deaths in America than you have in, say, England or, for that matter most other so-called 'First World Countries.'