Laser aiming module
From Halopedia, the Halo wiki
Laser Aiming Modules, otherwise known as laser sights, point lasers, or infrared pointers are weapon attachments used for sighting. These sights are used on M7 and M7S Caseless SMGs and M6C/SOCOM.[1]
They are mostly used for night operations where aiming with conventional sights would be difficult. With these "pointers", Special Forces such as the Orbital Drop Shock Troopers, as they are the primary users for such equipment, can align them to a target, making aiming easier. Another variant of this would be infrared lasers, such as the ones used on the Spartan Laser. Contrary to popular belief, the laser pointer will not draw a red line in the air towards its target, unless there is sufficient atmospheric disturbance, such as dust or smoke, between the pointer and the target.