Plasma Rifles are a common light weapon in the Covenant army, wielded primarily by Elites. It uses plasma technology instead of ammunition. This means that the weapon draws from a power source to generate its projectiles rather then firing individual missiles like modern guns. The weapon is known for its power and accuracy and its incredibly high rate of fire. However this high firing rate heats the weapon up and prolonged use of it will overheat the rifle rendering it useless for a brief period of time. The Plasma Rifle can fire approximately 300 shots of plasma. It is said that the weapon's power source can be replaced when depleted, however the Humans in the Halo Universe lack the knowledge to do such things. Because of this, the Master Chief and other human users of the weapon must abandon it when low or depleted of energy. The ability to play as the Covenant Elites soldier in Halo 2 does not bring with it the ability to "reload" the weapon; users must still abandon the weapon when out of power. However it is known that the Covenant army is adaptive rather than inventive and therefore the knowledge of how to reuse this and other plasma weapons when depleted of energy may also be lost to them. The plasma rifle appears in both Halo games, although with some slight changes between the two games.
Halo: Combat Evolved
The plasma rifle in the original Halo game is somewhat more powerful and accurate then the version in the sequel. Furthermore the weapon held a unique ability to stun opponents that were hit by the high velocity plasma rounds that the weapon fires. This effect greatly reduces the victims ability to move and dodge the in coming projectiles and allows the wielder of the plasma rifle to more easily hold the opponent in the weapon's firing arc. The drawback, however, was that this effect is only felt when the weapon is fired in its automatic mode. Therefore while the opponent was much easier to repeatebly hit while stunned the weapon will often overheat before the opponent was completely killed. However despite this drawback the stun ability is a useful and potent feature in the hands of an experienced user.
Halo 2
The plasma rifle in Halo 2 is not as powerful or accurate as its predecessor. It also lacks the ability to stun. However these draw backs are compensated by the ability to duel-wield the weapon. This allows the rifle to be pared with a wide variety of other weapons from Halo 2. This means that the weapons power and firing rate can be added to other weapons to create powerful combinations. The changes in the weapon are directly related to the inclusion of duel-wielding in Halo 2. For purposes of balance, the weapon, along with many others from the original Halo, was tweaked to better fit the new game's fighting style.
Plasma rifles are also the basis for several other weapon systems, including the plasma turrets on a Wraith and Ghosts.
The Plasma Rifle is not to be confused with the Brute Plasma Rifle, which is red instead of blue, and considerably different.