X23 Non-Nuclear Electromagnetic Pulse Cannon
From Halopedia, the Halo wiki
File:Th gremlin.jpg
The X23 NNEMP Cannon takes up much of the Gremlin's dorsal surface and is much bulkier than the far smaller and more portable W/AV G/GNR.
The X23 NNEMP Cannon is a weapon in service with the UNSC Marine Corps. Gremlin support vehicles are equipped with one of these turrets for anti-armor combat.[1] Since it uses EMPs, this weapon is ineffective against infantry.
