Needle cannon

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 out the Heavy Needlers. The Heavy Needlers on a Enforcer shoots out blood red needles instead of the weaker deep purple variety that the Covenant use. These needles also tend to be larger than the Covenant needles that are shot out the lesser Needler. The Heavy Needlers needles do not explode but still pack quite a punch and can take down the Arbiter quickly. Even though the standard Covenant Needler is weaker, the Covenant also have another variant that is surprisingly more powerful than the variant that Sentinel Enforcers fire. In Halo: First Strike it mentions, "A hail of purple-white crystalline shards hissed through the air, arcing up from the forest beneath them. Each shard looked like the projectile fired from a covenant needler-but far larger. The shard that slashed past Fred's cockpit was the size of his forearm.".

Its is Also belived that the larger covenant needler is the one seen on shadows and scarabs in halo 2.