H-165 Forward Observer Module

The H-165 Forward Observer Module, commonly referred to as the H-165 FOM, Target Locator or Designator is a United Nations Space Command piece of equipment.

Design details
The H-165 FOM is a compact, handheld laser device designed for acquiring and designating targets for small-scale orbital bombardment from an orbiting UNSC starship. While similar in function to the laser designator, the Target Locator is much smaller and can be held with one hand. The Target Locator also features a scope for target acquisition accuracy at greater range and an intercom for user communication.

Operation
When the trigger is held down for three seconds, a green laser beam marks the targets, and a red circle is projected on the ground around the target area. Once the target has been locked, seven missiles strike the designated area from above, doing a large amount of area damage.

Trivia

 * Destroying two vehicles with a single shot from the Target Locator in the third Campaign mission unlocks the Achievement "Two Corpses in One Grave." This achievement's name is reference to a line spoken by the Gravemind and is similar to the Halo 3 Achievement "Two for One."
 * The Target Locator is available only in Firefight and Campaign. It does not appear in Matchmaking or Forge, presumably for balancing reasons.
 * The Target Locator is the only weapon in the game which will not have infinite ammunition from the infinite ammo selection in custom Firefight matches. A detached turret will also not have infinite ammo unless the bottomless clip selection is enabled, unlike the Target locator which will still not have infinite ammo.
 * In the E3 Firefight demo, the Target Locator was labeled as the "Laser Designator" when a player picked it up. In the final game, it is labeled as the "Target Locator". Also, the Locator projected a blue circle on the ground when locked on, the color of wich was changed to red in the final game.
 * Normally the Target Locator cannot be given to AI allies but it can be glitched into their hands, allowing it to be used limitlessly.
 * On the Firefight map Unearthed the Target Locator has 3 shots rather than the usual 2. The Target Locator will also have 3 shots in Campaign if ONI: Sword Base is started from Rally Point Alpha.
 * While zoomed in with the target locator, holding down the right trigger will show the word 'acquiring' on the lower left corner of the HUD, although it is misspelled as 'aquiring.'
 * A Target Locator is capable of locking on to a shot from a Concussion Rifle or dropship.
 * If the Target Locator is the player's "Tool of Destruction" as listed in the post-game carnage report, it will be referred to as "Airstrike".

List of appearances

 * Halo: Reach