The needler

A Needler is a Covenant projectile weapon that fires long and very sharp shards that are guided until they impale a target — hence the “needler” moniker — several seconds after coming to rest in their target the needle shard detonates creating severe and in most cases fatal wounds. The needler takes a general shape of a V with the top and bottom part of the weapon curved. The weapon takes on a Purple/Pinkish color, and has 14 holes on the top, with the needles protruding out of the holes. When the trigger is pulled the needle is somehow fed from the top into the "barrel" of the weapon, and fired at high speeds. The Type-33 GML is issued to lower and higher ranking infantry in the Covenant, Grunts (and jackals in Halo 3: ODST) are commonly seen wielding this weapon, however higher ranking forces like Elites (and several low ranking Brutes in Halo 3: ODST) are seen using this weapon, Drones are also fond of this weapon, and their efficiency with it is high as their flying capabilities and large numbers make the needler harder to dodge. Though not generally considered effective enough to be a combat multiplier, the wounds this weapon inflicts are horrific. When the trigger is held down, the rate at which the 'needles' are fired increases. However, in Halo 2, the rate stays the same.
The needler is one of the most unusual weapons in the Covenant arsenal and the least understood, how the weapon functions and how the shards are able to track their targets remains a mystery to human military experts and scientists. Like all Covenant weapons, the needler still uses an Energy Coil to power and fire the weapon, should the coil fail the weapon is rendered useless.I have got this info from halopedia.com

The M6 spartan laser

The M6 Spartan Laser is a man-portable, shoulder-fired, directed energy weapon used by the UNSC. When the trigger is pulled, a red targeting Laser is painted on-target accompanied by an audible whine as the weapon cycles up. The Spartan Laser will then charge for approximately three seconds before discharging the main laser. As the Spartan Laser charges, the charging tone gets noticeably louder up until the laser is fired. The firing sequence can be aborted without discharging the battery as long as the weapon is not actually fired; for example, if the target moves out of sight or the operator needs to displace. The laser is capable of penetrating several enemies or vehicles, and has a small blast radius, injuring targets within two meters of the point of impact and toppling light vehicles. It has an offline sequence between shots while it (presumably) cools down (approx. 2-4 seconds), and is highly effective at destroying enemy vehicles.[2]
In Halo 3 Multiplayer, if you kill another player with the Spartan Laser, you will receive a medal, the Laser Kill Medal. It is likely awarded due to the difficulty of having to charge and aim the weapon. Also, the achievement "Two for One" is unlocked by scoring a double kill with a single laser shot in any ranked free-for-all playlist.
The weapon is not available in the campaign until the level The Covenant, which Master Chief begins the level armed with the Spartan Laser. There is another Spartan Laser lying nearby on the ground, presumably dropped by a Marine, but only if played on Easy or Normal. The M6 is the only weapon able to harm 343 Guilty Spark on the final level of Halo 3, with the exception of the Fuel Rod Gun and Rocket Launcher, through a glitch that Bungie has removed.
The way it damages is by multiple attacks (obviously with extremely little time between them). It isn't a one-hit attack as it generally appears to be. It could also be said that the more time you're in the laser fire, the more damage it accumulates. If you're barely stroked by the laser (especially if you're in a speedy vehicle), you may survive. Evidence to this could be how you can shift the laser a bit during mid-shot (during the time the actual laser is shot).I have got this info from halopedia.com

The BR55HB SR

The BR55HB SR is a select-fire rifle that has been in service for over 27 years. The UNSC employs the Battle Rifle as a medium range marksman rifle, it fires new 9.5x40mm ammunition from a 36 round magazine, which fits flush in the receiver. The magazine housing is built directly into the underside of the stock of the rifle and is located behind the grip. This titanium alloy weapon is gas-operated with a rotating bolt and therefore must be charged before the first round can be fired. The charging handle used to chamber the round is located on the left side of the weapon and does not move during operation, but is pushed back during reloading. The rifle has a housed magazine in the stock. The ejection port is located on the right side of the weapon. The BR55HB SR, has noticeable changes from the BR55. It has a longer barrel for increased range and accuracy. It is also fitted with a Trijicon ACOG-style scope on a modified carrying handle and now also has a trigger guard. The safety is also located above the handle of the weapon.
It is never stated exactly what the maximum effective range of the BR55HB SR is. The MA5C Assault Rifle, which was described as most suited for short to medium range, as opposed to the Battle Rifle's mid to long, has a maximum effective range of 300 meters and the Covenant Carbine, which is similar in use with the Battle Rifle, has a maximum range of 600 meters. It is stated that the Battle rifle could reach up to 900 meters with deadly accuracy; however, that may have been due to the design of the prototype Battle Rifle, deployed in 2524, the field issued Battle Rifle may not have that type of range.I have got this info from halopedia.com

The M41 SSR

The M41 SSR is a heavy ordnance weapon in the UNSC arsenal that fires a 102mm Shaped-Charge High-Explosive Surface to Surface Missile. The launcher sports a 2x scope and can fire rockets over long distances with devastating accuracy, although its altitude decreases over longer distances, this model is not to be confused with the M19 SSM Rocket Launcher. The M41 is, however, identical to the M19 variant rocket launcher. The M41 uses a unique design then any other rocket launchers. When reloaded, the barrels are removed, two preloaded barrels are then inserted back onto the unit. With this mechanism, a Marine can greatly reduce the weight he carries without throwing the weapon away like some contemporary disposable rocket launchers. This setup is very similar to that of the Javelin Anti-Tank System currently used by the U.S. military.I have got this info from halopedia.com

The HMG

The AIE-486H Heavy Machine Gun is a standard Gatling-style heavy machine gun, used by the UNSC for offensive and defensive purposes. It is also more powerful than the UNSC's stationary turret, the M247 GP Machine Gun. It has saved many lives with its defensive capabilities holding enemy forces at bay for a limited time during the battle of Reach, accounting for many casualties to the Covenants efforts to take out the Orbital MAC Generators.
For defensive purposes, it can be mounted on a tripod, but when used for an assault it can be irreversibly and quickly detached from its tripod by a SPARTAN-II or Elite's brute strength. In its unmounted form, the weapon has a limited ammunition capacity of 200 rounds and takes about a second to "spin up" before reaching its highest rate of fire. Pulling the trigger once will cause the gun to fire a maximum of two rounds at a moderate rate; holding it down builds up the rate of fire to a higher rate.
The gun slowly climbs during automatic fire like the M7 Caseless Sub Machine Gun, but its recoil is lessened by the gun's weight, which makes it hard to move around as well as decreasing the user's speed. Unlike most mini-guns in other games, the AIE-486H does not overheat with continuous fire. This is a more realistic feature as having three barrels on the gun disperses the heat equally within each barrel; allowing the gun to remain cool and continue functioning.Ammunition
The AIE-486 fires 7.62x51mm Saboted Light Armor Penetrator rounds at a high rate of fire. The SLAP design incorporates a polymer sabot, which allows for the use of a tungsten penetrator projectile of a lesser diameter than the original bore. By using the casing of a large cartridge with a lightweight projectile, the velocity of the projectile is greatly increased. The bullets are powerful enough to punch through the armor of a Warthog or a Wraith and destroy it with ease.I have got this info from halopedia.com

The M6D pistol

he M6D Pistol is an 'up-sized' UNSC handgun issued to Navy officers, this model has been upscaled for use by SPARTAN-IIs in MJOLNIR armor. Even though the Spartan issue pistols are larger than the standard-issue variants (~117%) they can still share magazines. [3] The M6D is a semi-automatic, recoil-operated, magazine-fed, large-bore handgun that is controllable even during rapid fire, although at the cost of accuracy. It is most likely striker-fired, due to there being no visible external hammer. It fires M225 SAP-HE (Semi-Armor Piercing, High Explosive) rounds from a 12-round magazine. Operators can achieve an effective rate of fire of 3.5 rounds/sec or 210 rounds/min. The weapon is very accurate out to its maximum effective range. This accuracy allows incredibly precise target engagement at long range. This, combined with its decent damage against Energy Shields, makes it a viable option when faced with shielded opponents, such as Elites. It is, however, even more effective against unshielded infantry targets, being able to kill most targets in one shot to the head or two to three shots to the body.
The M6D is semi-automatic weapon - this principle of weapon operations means that the weapon will cock itself after every shot due to recoil and will continue to do so until the magazine is empty. The M6D also uses the short recoil principle; it uses the force of the recoil to eject the spent casing, chamber another cartridge, and re-cock the weapon so that it may be fired again. Before the first round can be fired however, a round must be chambered, this is done by inserting a loaded magazine into the grip of the weapon and then by pulling the slide back completely and letting it slingshot forward, which takes a round from the top of the magazine and carries it into the chamber. To reload, the empty magazine must be removed with the magazine release button located on the grip and a fresh magazine inserted. Once the fresh magazine is inserted, the slide is allowed to return to its normal position by the operator. There is no need to re-cock the weapon. Cocking is only necessary when chambering the first round when bringing the weapon out of "safe" mode - safety on, uncocked, unloaded.
The M6D is a very basic pistol compared to most 26th century technology. It is a large handgun, having an overall length of 26.7cm and possesses a rifled barrel, improving accuracy by spinning the bullet. It is issued in a hard chrome finish color and operates like most contemporary pistols. It has rear sights but it does not have a forward sight blade, which is replaced by the smart-link scope. It features a KFA-2 2x optical, smart-linked scope. This scope links directly to a users HUD or a Marine eye piece. It also has a large grip guard, which helps prevent the user from dropping it and a chrome barrel which helps prevent corrosion.I have got this info from halopedia.com

The MA5K

The MA5K is a cut-down version of the standard MA5B Assault Rifle. The weapon is most likely lighter and easier to carry than larger assault weapons, and so it is possibly appropriate to call it a carbine. Aesthetically, it is like a cross between an MA5B ICWS Assault Rifle and a BR55 Rifle, although the MA5K functions more like an Assault Rifle. It features a stripped-down design that appears almost skeletal.
Based on current-era tactical philosophy, it is believed that the MA5K version, was produced specifically for Special Operations forces because of its lighter frame, which allowed for more quick maneuvering and less visible profile, and probably for its lighter aural signature, which suits the requirements of commando missions well. This would make it perfect for Marine Shock Troops and vehicle crews as well, since it would not take up much room inside the vehicle.I have got this info from halopedia.com