Melee Weapons

Chain Weapons: Chain Weapons are any of a class of weapons that possess motorised biting teeth that saw and slash through the enemy, in a similar fashion to chainsaws. The teeth themselves are fashioned to be incredibly sharp, in some cases carrying a monomolecular edge, and are capable of slicing through steel bulkheads.The most common form of chain weapon is the Chainsword, frequently carried by Assault troops and low-ranking officers of the Imperial Guard and Space Marines (including the Traitor Legions); but it is sometimes seen amongst other races, notably the Striking Scorpions Exarchs of the Craftworld Eldar and elite Orks. Another common variant is the Chainaxe, which is usually carried by Chaos Space Marines (normally of the World Eaters Legion) known as Khornate Berserker, as the Chainaxe was once a standard-issue close combat weapon for Assault Marines during the time of the Great Crusade. Such is the skill of these Berzerkers and the weight of their massive Chainaxes that the axes are nearly as powerful as the much-feared Power Weapon.

Power Weapons: Power Weapons are rare and greatly coveted personal close combat melee weapons that are used on the battlefields of the 41st Millennium. Few members of the Adeptus Mechanicus retain the knowledge necessary to make these deadly weapons, and those that are in existence are often hundreds or even thousands of standard years old. Only the most powerful and influential members of the Imperium possess a power weapon as a result. Inquisitors and high-ranking Commisars or Imperial Guard officers tend to possess them, as do members of various noble families with potent political clout and wealth. The Space Marines make use of many of the power weapons in existence, as is their right.

Force Weapons: Force Weapons are advanced, psychically-attuned close combat weapons that are only effective in the hands of a psyker. Force Weapons effectively act as deadly, psychic extensions or amplifiers of the wielder's own Empyrean-spawned powers. They are designed to allow a psyker to channel deadly Warp energies into their victim, acting as a conduit between the wielder's mind and the flesh of his target. Large alien monstrosities and daemons that are resilient to conventional weapons can be slain outright by a single wound from a Force Weapon, as their bodies and minds are destroyed by the unearthly powers of the Immaterium.

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Low-Tech Weapons: Basic hand weapons are a common sight throughout the Imperium, and in many places it would be unthinkable to venture forth without at least one such weapon visible on your person. Depending on the planet's level of technology-- and the wealth of the user-- these can range from simple metal swords to high-tech blades made of exotic materials.

Ranged Weapons:

Las weapons: Laser Weapons, or Las Weapons as they are known in the Imperium of Man, are a family of directed energy weapons that produce beams of high-intensity amplified light to produce heat damage on a target. Laser Weapons are relatively easy to produce and maintain. No solid ammunition is ever used -- only power cells which can be recharged and quickly swapped with a fully-charged power cell. This makes them ideal for large troop formations like the Imperial Guard. While the accuracy of the laser beam can not be distorted by wind like slug ammunition, it can however be more quickly diffused by heavy particles in the air such as smoke and hence lose its power over long distances. Certain types of lasgun have specific uses, most notably the more powerful long-las which is the catch-all term for sniper variants because they bear longer barrels.

Solid Projectile Weapons: Solid Projectile Weapons or slug throwers are ballistic ranged weapons which use solid-slug ammunition and thus are the equivalent of third millennia military-grade firearms. They are found in pistol, rifle or cannon form. Auto Weapons are still popular amongst soldiers of the Imperial Guard; and the Autogun was the standard-issue weapon for the troops of the Imperial Army and the Imperial Guard until the start of the 32nd Millennium. While Autopistols and Autoguns are similar to their laser-variants (the Laspistol and Lasgun), Autocannons are very unlike Lascannons. Autocannons are rapid-fire ballistic heavy weapons designed to eliminate heavily armoured infantry or light vehicles, and are often used by the Imperial Guard's heavy weapons teams in battle, due to their versatility and reliability. There are also sniper rifles which use solid slug ammunition -- although, like other Auto Weapons, they are restricted by their use of heavier ammunition. The advantage the Sniper Auto Weapon has over its photon-based counterpart is that fewer enemies will recognise the report of the rifle, as opposed to the Long-Las' distinctive ruby beam.

Bolt Weapons: The Bolter, and its variants are some of the most powerful hand-held ballistic anti-personnel weaponry in use by the military forces of the Imperium of Man. It is a powerful assault weapon that fires explosive kinetic rounds colloquially referred to as bolts. The Bolter is a weapon synonymous with the Adeptus Astartes, and rightly so. However, although the Space Marines are its primary users, the Bolter finds itself in use in military organisations throughout the Imperium. The weapon is fearsome, with explosive rounds capable of ripping through or blowing apart a foe. The Chaos Space Marines of the Traitor Legions were issued their Legions' Bolters before the Horus Heresy, and therefore, use generally older variants than the patterns available to present-day Loyalist Space Marines.

Melta Weapons: Melta Weapons are a type of Imperial plasma weaponry that make use of a miniature fusion reaction to produce a blast of intense, searing heat. The Meltagun and Multi-melta (also known as "Cookers" or "Vape Guns"), as well as the grenade-like Melta Bomb, are formidable plasma-based directed energy weapons. Melta Weapons have a short range but are very powerful and their thermal blast's intensity increases as the distance to the target decreases. A Meltagun works by inducing a minute, sub-molecular nuclear fusion reaction within a highly pressurised pyrum-petrol fuel mix located within an ammunition canister, and then projecting the resulting plasma through the cannister and from the weapon's barrel as a blast of incredible heat. Melta usage is accompanied by a distinctive hissing sound as the beam boils away the water in the air, then a roaring blast as the beam reduces the target to charred scraps or molten slag. Meltas are the premier anti-armour weapons, and few if any armoured vehicles can withstand their power.

Plasma Weapons: Plasma Weapons are highly potent and destructive directed energy weapons utilised in many forms by the advanced intelligent races of the Milky Way Galaxy. Most Plasma Weapons work by delivering pulses of searing energy and superheated matter that have been transmuted into a gaseous plasma state that carries an electrical charge. The plasma "bolts" fired by these weapons explode on impact and generate the destructive heat of a small sun, and the sheer amount of energy released by the impact of superheated plasma is often enough to completely vaporise the target. Plasma Weapons vary greatly in form and size; ranging from small and compact Plasma Pistols to huge starship batteries that can obliterate entire cities in a single salvo. Against all forms of armoured infantry and light vehicles, the superheated bolts fired by smaller Plasma Weapons impact with the fury of a supernova, scything through steel, flesh and bone as if they were nothing.

Flamer Weapons: Flamer Weapons are flamethrower weapons, capable of unleashing a liquid incendiary chemical that bursts into flames as it leaves the weapon. Dlame-based weapons are used by several of the intelligent races and their militaries across the Milky Way Galaxy, and are valued for their ability to destroy many enemies at once with a burst of expanding flame, regardless of any protective cover they possess. The most common forms of Flame Weapons are Flamers and the more compact Hand Flamers, both of which are considered assault weapons due to their relatively short range. Loyalist Space Marine and Chaos Space Marine Flamers work by firing a mix of highly volatile liquid chemicals which ignite with the use of a pilot light. This flaming chemical sticks to its target and continues burning on its own accord - those who are not killed instantly die horribly as the super-hot chemical continues to burn through their bodies. The most common flammable substance used as Flamer fuel is Promethium, which is a petroleum-like jelly that can stick to a target and is very similar to the twenty-first century incendiary called napalm. 

Low-Tech Weapons: Even in the 41st Millennium there is a call for low-tech weapons,found on feral, undeveloped planets or post-apocalyptic 

There are lots of different types of weapons in the 40k universe. Being Imperial Guard, you will be using Imperium of man technology. It has not changed in thousands of years so its usually reliable but not always the most advanced. There are 2 main types of weapons, ranged and melee. Below is a brief description of each weapon type.

Weapons