Needle cannon

The Heavy Needler is a much larger and more powerful version of the Covenant Needler found on certain vehicles and turrets.

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. Also, 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 in Halo 3.