The Needler was the only Covenant weapon in Halo 1 that had ammunition; all the other weapons had batteries that drained and became useless to the player.

In single player it was useful for taking out Elites; in multiplayer it was thought too weak, with projectiles that were too slow and too easy to dodge.

In Halo 2, the Needler's projectiles are supposedly faster and pack more punch, although some players have reported that Needler rounds slowed between the E3 2004 and final builds of the game.

The Needler can be dual-wielded and fires in semiautomatic and automatic modes.

Plasma turrets are stationary guns, usually used by Covenant to defend strategic positions. In Halo 1, the users of these guns were especially vulnerable to snipers, Banshees and grenades. For Halo 2, it appears as if the turret (also called a Shade) has gotten a serious makeover, in addition to getting a plasma shield, which the first iteration did not have.

The Carbine is thought to be a Covenant equivalent of the battle rifle. It cannot be dual wielded, and has a zoom that when used, limits its rate of fire. It is assumed it will be wielded by upper echelons of the Covenant hierarchy, such as Elites, or possibly by Drones.

Dormant until activated, Covenant plasma grenades will "stick" to targets, killing most targets (in Halo 1, anyway) and causing damage to nearby units, including disabling shields. As in the first game, you can carry up to four of these. In the first game, they were carried by both Grunts and Elites.

The plasma grenade has a blast radius of 30 feet, and detonates three seconds after coming to rest.

UPDATE: This weapon will also be in Halo 3. Any changes to specifications are as of yet unknown; however, indications are that because of the addition of Spike Grenades, the number of Plasma Grenades that can be carried at once will be reduced from four to three.

UPDATE: In the Halo 3 Public Beta, the number of grenades per type that can be carried simultaneously is in fact two.

In Halo 1, the plasma pistol was carried mainly by Grunts and Jackals. With each squeeze of the trigger it produces a small bolt of plasma that damages opponents or drains their shields. When the trigger is held down, it produces an alternate-fire mode where a large burst is fired, seeking targets within range and eliminating shielding on targets like Jackals, Elites, and Spartans. It was the exclusive weapon for Jackals, who carried no other weapons in the first game, while Grunts sometimes carried Needlers or even FRGs.

In multiplayer, this weapon, like the larger plasma rifle, produces a stunning effect, slowing the movement of opponents.

This weapon returns, apparently unchanged in Halo 2. There is some debate over whether or not the stunning effect persists.

Like most Covenant plasma based weapons, the pistol has a charge level. When this charge is drained, the weapon becomes useless. In Halo 1 it was not possible to recharge this weapon, and there is no indication that Halo 2 will be any different.

When firing the weapon heats up; if it gets too hot, it cannot be fired and must cool. It has a meter that indicates temperature. After firing an overcharge (alt fire) blast it must cool. It can fire at a fairly high rate in semiautomatic mode, and does not have a fully automatic mode. The overcharge mode drains the weapon's charge more quickly than the semiautomatic mode.

The plasma pistol can be dual wielded.

This weapon, apparently carried by the apelike hairy Brutes seen in the E3 2003 trailer, features a vicious-looking wide blade on the handle, presumably for melee attacks, and operates as a kind of grenade lobber.

It cannot be dual wielded, and is the only Covenant projectile weapon (unless you count the Needler).

The preferred weapon of Elites in Halo 1; in fact, no other Covenant species in the first game would use it, although Flood combat forms created from Elites and Human marines would also use them.

This weapon will fire continuously if you hold down the trigger at the expense of accuracy, as with most weapons that can be fired this way in Halo. Like the plasma pistol, it has a non-rechargeable battery. It has no other firing modes and its projectiles do not seek.

Some screenshots have shown Jackals holding plasma rifles in Halo 2.

The plasma rifle can be dual wielded, contrary to what it said earlier in this space; as noted below in several comments, there are screenshots that show it being dual wielded, and Bungie's own Dual Wielding Guide, published today, also confirms that the Plasma Rifle is dual wieldable.

As with other plasma weapons, it has a battery that drains as it is fired. When fired too quickly or too often, the weapon overheats and must cool. A temperature gauge indicates when this is about to happen.

The plasma rifle can be fired in semiautomatic and automatic modes.

There is no further information regarding any possible changes to this weapon for Halo 2; it is assumed to be principally the same.

In Halo 1, some Elites eschewed carrying ranged weapons like plasma rifles or needlers, instead opting for the plasma sword, which was essentially a one-hit-kill weapon. It was first seen in the E3 2000 trailer, where it is used both by Elites and by the Master Chief.

Sadly, in Halo 1 the player was unable to pick up or wield this weapon, which evaporated after being dropped.

In Halo 2 campaign and multiplayer, this weapon can be used. It has a lock-on mode that delivers one-hit kills at close range. It cannot be dual wielded. In campaign mode, it has a battery than expires. In multiplayer it can be used indefinitely.

One may assume that the Master Chief will also be able to use the sword in campaign mode should he come across it, but so far information about most aspects of campaign mode is limited, so this has not been confirmed.

The sword is approximately 3 feet in length and was originally assumed to be purely ceremonial in nature.