A weapon is an instrument used for the purpose of causing harm or damage to people, animals or structures. Weapons are used in hunting, attack or self-defense and range from simple implements like clubs and spears to complicated modern machines such as intercontinental ballistic missiles. One who possesses or carries a weapon is said to be armed.

Ammo ...
Guns ...
Knives ...

Weapon Classifications

By user

Personal weapons (or small arms) - designed to be used by a single person.
Hunting weapon - primarily for hunting game animals for food or sport
Infantry support weapons - larger than personal weapons, requiring two or more people to operate correctly.
Fortification weapons - mounted in a permanent installation, or used primarily within a fortification. Usually high caliber.
Mountain weapons - for use by mountain forces or those operating in difficult terrain. This includes modifications of existing weapons for paratroopers.
Vehicle weapons - to be mounted on any type of combat vehicle.
Railway weapons - designed to be mounted on railway cars, including armored trains.
Aircraft weapons - carried on and used by some type ofaircraft, helicopter, or other aerial vehicle.
Naval weapons - mounted on ships and submarines.
Space weapons - are designed to be used in or launched from space.

By function

Antimatter weapons (theoretical) would combine matter andantimatter to cause a powerful explosion.
Archery weapons operate by using a tensioned string and bent solid to launch a projectile.
Artillery are firearms capable of launching heavy projectiles over long distances, which can explode on impact.
Biological weapons spread biological agents, causing disease or infection.
Chemical weapons, poisoning and causing reactions.
Energy weapons rely on concentrating forms of energy to attack, such as lasers or sonic attack.
Explosive weapons use a physical explosion to create blast concussion or spread shrapnel.
Firearms use a chemical charge to launch projectiles.
Improvised weapons are common objects, reused as weapons, such as crowbars and kitchen knives.
Incendiary weapons cause damage by fire.
Non-lethal weapons are designed to subdue without killing.
Magnetic weapons use magnetic fields to propel projectiles, or to focus particle beams.
Mêlée weapons operate as physical extensions of the user's body and directly impact their target.
Missiles are rockets which are guided to their target after launch. (Also a general term for projectile weapons).
Nuclear weapons use radioactive materials to create nuclear fission and/or nuclear fusion detonations.
Primitive weapons make little or no use of technological or industrial elements.
Ranged weapons (unlike Mêlée weapons), target a distant object or person.
Rockets use chemical propellant to accelerate a projectile
Suicide weapons exploit the willingness of their operator to not survive the attack.
Trojan weapons appear on face value to be gifts, though the intent is to in some way harm the recipient