Needle cannon

The Heavy Needler is a much larger and more powerful version of the Covenant Needler.

Description
It is featured in Halo Wars, and is the main weapon of the Vampire, a Covenant Air vehicle. The Heavy Plasma Turret can be upgraded to feature this weapon as well if you choose to upgrade the turret with an Anti-Air weapon.

It was vaguely mentioned in The Fall of Reach, described as a large version of the normal needler round.

It is most likely an effective AA weapon due to the Needle's tracking abilities making it a whole lot harder to dodge, while still causing heavy explosive damage.

Trivia

 * It seems the Heavy Needler is replaced by the AA Wraith Fuel Rod Cannon as an anti-aircraft weapon.