Needle cannon
From Halopedia, the Halo wiki
Introduction
The Heavy Needler is first seen in Halo 2 on the level Sacred Icon, as Tartarus explains to you how to take down a Sentinel Enforcer. If you stay alive long enough, the Enforcer will start to shoot at you with its Heavy Needlers, which fire crimson needles that are larger and more powerful than the weaker purple variety found on the Covenant weapon. These needles do not home in on a target or explode on contact, but still pack quite a punch and can take down the Arbiter after a couple of direct hits. This weapon is particularly useful against the hordes of Flood that the Sentinels face and was most likely developed specifically for combat use against the infected lifeform.
Use
The Enforcer will only engage targets with the Heavy Needler that are few and far between, such as the Arbiter, and very small groups of Flood. The Enforcer is not known to otherwise engage targeted hostiles with this weapon.
