Beamos

Beamos are impregnable statues with rotating heads and a single, glaring eye, that have appeared as dungeon staples as early in the Zelda franchise as A Link to the Past. These foes will not hesitate to fire an energy beam at anything that makes eye contact with them, or comes within close proximity.

Characteristics
The Beamos is one of the most technologically-advanced enemies in the Zelda universe, if not the single most. This foe is not only made of solid metal, as in Ocarina of Time, The Wind Waker, and in Phantom Hourglass, or stone like in Twilight Princess, but wields and uses a finely-tuned laser to attack territorial threats, situated at its "forehead." Despite the modern look and attributes, these foes cannot move, and must rely on their laser solely to keep intruders at bay. For this reason, Beamos are often situated inside dungeon rooms, or placed strategically on a staircase or entrance to impede progress, using swiveling movements to check all of their bounds. This laser of theirs, in every incarnation, has a specified range that can be bested whenever Link steps out of range, hides behind an or when speaking in terms of Link's Awakening, the Oracle titles, or Phantom Hourglass, simply when the Beamos is off the screen.

The laser of the Beamos cannot be avoided once it has been shot, however, in Link's Awakening, Link can use the Mirror Shield to reflect the laser away. In that same vein, for the majority of Zelda titles, the laser itself is a continuous beam, save for A Link to the Past where it is a single quip at a time.

Variations
Beamos across the Zelda series often only come in one variety, however, in games like The Wind Waker, which denotes Beamos' by color, and Ocarina of Time, that distinguishes these foes by size, there is quite the variation. In The Wind Waker, they come in two variations: red ones, which act like normal Beamos, and blue ones, which have fixed beam paths, blocking Link's path entirely, until they are destroyed. In Twilight Princess, they come in two variations, as well: a larger brown type found in the Goron Mines and minor caves is able to shoot fire beams, and a thinner white type, similar to a Doric pillar, in the Temple of Time, carries the ability to shoot pink beams of energy. These white variants cannot be moved and can be fully obliterated by the statue Link controls with the Dominion Rod.

Weaknesses
Beamos, series-wide, have a collective weak spot centralized at the eye from which its laser is produced, however, its the method of fracturing that eye that provides the variation between games, of the species that can be destroyed that is. The Beamos variety seen in Link's Awakening and several subsequent titles cannot be destroyed, but avoided. Straying from the norm, the Beamos of Ocarina of Time, Majora's Mask, and The Wind Waker' can all be annihilated with the use of bombs, exploding on contact. The bomb strategy is replaced with that of a Bombchu in Phantom Hourglass.

In Twilight Princess, they can be defeated with an arrow to the eye, as in Phantom Hourglass as well, or by using a Dominion Rod-possessed statue to smash them in the Temple of Time. If Link is out of arrows, he can also defeat them using a well timed strike from the Ball and Chain.

Trivia

 * In Ocarina of Time, when targeting a Beamos, Navi says that it doesn't like smoke. This quote is similar to the Old Man's "helpful" hint in the Moon Labyrinth in The Legend of Zelda, where he says that "Dodongo Dislikes Smoke."
 * The Beamos, Dexivines and battleships in The Wind Waker are the only enemies in the game that cannot be made into a Nintendo Gallery figurine. Strangely, giving a picture of one to the sculptor in the Nintendo Gallery will result in him saying that he already made one.