These are the currently known weapon we can deduce from all the videos and off the official Halo 4 website, forgive me if some names are slightly wrong, this will be updated as soon as possible. Feel free to post comments about these weapons too. As it all helps.
So far confirmed are the following weapons (and grenades)
UNSC Arsenal:
Assault Rifle
The assault rifle is the bread and butter of the UNSC weapon pool, it is cheap to produce, and can fill the air with bullets. Use this for up close targets. It carries 32 rounds per magazine.
Magnum Pistol
The primary sidearm weapon of the UNSC, the Manum Pistol is great at short to mid range and can easily overwhelm a non-shielded opponent. With 12 bullets per magazine this sidearm can be switched to when a primary weapon runs out of ammunition, to finish the job as it were.
Sticky Detonator (Rocket/Grenade Pistol)
The sticky detonator is a grenade launcher type weapon that allows the user to manually hold the trigger and detonate on command. Direct hits are lethal, but require a steady aim. Useful for setting up traps on weapon drops and key choke points.
Battle Rifle
The Battle Rifle is the go-to weapon of choice for short to mid range engagements, due to it's semi-automatic burst fire and head shot capability, this accurate firearm is a deadly combination. Proving to be superior to the assault rifle and much more versatile the battle rifle is the prefered weapon for just about any engagement. Each magazine sports 36 bullets, giving the user 12 three-round burst for sustained firepower.
DMR Designated Marksman Rifle
Very similar to the battle rifle, but much more clinical in it's execution, the DMR fills the gap for a short-mid to mid- long range rifle. Sporting a single fire action means the user ideally wants to pick of distanced targets rather that a nearby antagonist. The DMR is a precision rifle for those who lean more towards the sniper side of the action. Having 15 rounds per clip means the stopping power and sustainability during combat is high.
Rocket Launcher
The rocket launcher is the support weapon of choice. A dual tube barrel allows two shots before reloading is required. New ordnance leaves behind a white smoke trail, so beware that your location is betrayed. But with this weapon in your hands, you will remain in control of the immediate area and can easily defy enemy vehicle aggressors.
Sniper Rifle
The sniper rifle is still the master of range. And with 4 bullets per magazine you will not be short of opportunity to reign death on the enemy. However you will need steady hands to obtain those important head shots. Only skilled users allowed...
Spartan Laser
The spartan laser is the deadliest beam action weapon in the UNSC. Paint a target, hold the trigger to charge for two seconds and just watch vehicles disappear. Skillful users are able to take down enemy infantry aggressors at short, mid and long range.
Fragmentation Grenade
The fragmentation grenade is your standard issue ball of death. Skilled users can predict enemy movement (or lack of) and will ricochet off walls and obstacle to land a perfect grenade at their feet.
Covenant Weapons:
Plasma Grenade
The covenant plasma grenade reduces shielding very effectively and possesses the ability to stick or cling to a target. Whether the target be a vehicle or person, once stuck the opponent is usually dead.
Plasma Pistol
The standard plasma pistol is weak on its own, but if lots of these fire at you then take cover quickly. The party piece of this weapon is its secondary fire over-charged shot, which can eradicate a target's shields entirely. The combo of draining shields and then killing the target with a head shot via a Magnum or Battle Rifle may be considered cheap, but proves highly effective.
Storm Rifle
The Storm Rifle is the spiritual successor to Plasma Repeater, yet more refined. The longer barrel and better cooling mods allow for fully automatic quick and accurate plasma suppression. Nearby enemies will evaporate to the ensuing barrage. As per all plasma based weaponry, overheating occurs from vigorous use.
CovenantCarbine
The Covenant Carbine is very similar to the Battle Rifle and DMR. Whilst firing only single shots, the carbine can be fired extremely quickly. Factoring in the high accuracy and head shot capability as well, the carbine becomes a very effective short and mid-range weapon.
Needler
The Needler is a scary weapon in open or contained spaces. Each shot is fairly weak on it's own, however once several shards strike a target, a super-combine explosion destroys it's victim. This lethal effect and the natural ability of the shards to home-in on their target, makes the Needler an effective short to mid-range power weapon, especially if used in open spaces and internal areas with little cover.
Energy Sword
The Covenant sword is a power weapon that kills with a single strike. The lunge feature allows for a quick attack that is almost unstoppable. The sword has limited energy so can only be used for so long, although it is still very deadly non the less.
Forerunner Ordnance:
Scatter Shot
The Scatter Shot fires a direct beam of energy that kills personnel instantly. It is a close quarter power weapon that can ricochet off hard surfaces, making a precise user to be deadly without having a direct line of site with his opponent.
