Annihilator Beam

The Annihilator Beam is one of Samus Aran's beam upgrades, found only in Metroid Prime 2: Echoes. It is a secret Luminoth weapon that was installed on Quadraxis when it was built, before it was lost to the Ing Hive; therefore, upon defeating Quadraxis on Dark Aether, Samus acquired the beam. The Annihilator is powered by both light and dark energy.

Description
The Annihilator Beam's strength comes from its super-fast rate of fire, on par with that of the Power Beam, rather than its actual power level. Normal shots have a homing effect: even without a lock-on, the attack will automatically home in on a nearby target. This makes this beam extremely useful for taking down large hordes of small enemies, or firing barrages at more powerful foes while being able to dodge their attacks more easily. It uses a combination of both light and dark energy, and is similar in function to the Wave Beam in Metroid Prime in many ways, and the arm cannon takes on the same shape as the Plasma Beam from Metroid Prime. It is able to open the Gray Door (as colored on the in-game map) scattered around Aether, which are often shortcuts leading to certain expansions.

Uses
When fired at a Light Beacon or Light Crystal, the Annihilator Beam temporarily turns it into a Super Beacon or Super Crystal, respectively. These versions of Beacons and Crystals share their Energized (powered by a shot from the Light Beam) counterparts' ability to damage Ing and other Dark-based creatures, while Attracting them (powered by a shot from the Dark Beam). This capability is incredibly useful for making long fights against difficult Ing much shorter.

The Annihilator Beam requires both Light and Dark Ammunition to function properly, and uses one of each per normal shot. The Annihilator Beam can activate any rift, but cannot open the Purple Hatch or the White Hatch. The lacking part of the Annihilator Beam is that it's not as powerful as the Light Beam (at least against Dark enemies) nor the Dark Beam (against normal enemies).

Combined with the Echo Visor, it can interact with Echo Key Beam systems to open Echo Gates, another functionally shared with the Wave Beam.

The Annihilator Beam is particularly useful in defeating the Emperor Ing, as it damages it in all of its phases.

Disruptor
Its charge beam technique is called the Disruptor, which does not home in on targets, but offers a large blast radius and stuns enemies. It is interesting to note that the charged shot will destroy a War Wasp Hive, but will not dispatch the shell of a Brizgee; under normal circumstances, both are destroyed by the use of a Missile.

Charge Combo
Main Article: Sonic Boom

The Annihilator Charge Combo is the Sonic Boom, an exceedingly powerful shot that creates a rift in space and damages any enemies near the target. When activated, it instantaneously creates a rift at the closest target in the line of fire, making for a very fast and powerful attack. Interestingly enough, even though it is named the "Sonic Boom", it cannot be seen when using the echo visor, which allows the user to "see" sound. A likely functional reason may be that an object which creates a Sonic Boom, which by definiton travels faster than the speed of sound, could not be detected by a sound-based sensor if the Sonic Boom's direction of travel is oriented away from the sensor, as the initial SONAR pulse, traveling at the speed of sound, would be unable to catch up to the Sonic Boom.

Metroid Prime 2: Echoes Instruction Manual
"Fire streams of energy that seek multiple targets and emit sonic waves that can be used on sonic-powered devices. Its shots are effective against light and dark enemies. Charge it to fire a Disruptor shot that stuns enemies."

Trivia

 * In physics, the word "Annihilation" is used to denote the process that occurs when a subatomic particle collides with its respective anti-particle. Since light and dark can be seen as anti-particles (or opposites of each other) the weapon`s name may come from more then its destructive tendencies alone.
 * In the New Play Control version of Echoes, when Samus charges the Annihilator Beam and aims up, openings can be seen at both ends of the shock-absorber rings. This also happens with the Plasma Beam in Prime.
 * Despite having both Light and Dark qualities, it cannot open pure-colored doors (namely Purple Hatch or White Hatch). However, it can activate both colors of Portals.