Chaingun

This weapon has not been identified by Bungie but is informally known by fans as the "Chaingun". Video footage from twenty-four seconds into the Halo 3 ViDoc: Is Quisnam Protero Damno! is used as evidence of its existence. Although the weapon will presumably appear in Halo 3, little is known about it at this stage.

Behind the scenes
When this weapon first appeared in the ViDoc, some believed that it was the M41 LAAG from the Warthog. However, Frank O'Connor went on record as saying that the M41 LAAG could not be removed from the back of a Hog.