Usable Pelican turret
From Halopedia, the Halo wiki
Playable Pelican Turret on Long Night of Solace is an easter egg on the Halo: Reach campaign level Long Night of Solace.[1]
Walkthrough
After the Pelican carrying the Slipspace bomb enters the Ardent Prayer, the player can enter the cockpit and control the turret. To do so, they must crouch low along the side and keep pressing the button to enter, until they do so.
While inside the turret, the player has complete control of it and can fire it in any direction. Unlike most vehicles, however, the view is still first-person, and as such the player's vision will be heavily obscured by the turret itself. After a minute or so, however, the turret itself will disappear and the player will be able to see again, minus the temporary blocking by the firing flash.
The turret can be destroyed by enemies if the player is not inside, but once inside they are effectively invincible. It has been noted as a good way to finish off battles in the hangar on higher difficulties.
Related Links
Internal
External
Tyrant's Halo:Reach Mythic Guide, Halo.Bungie.org
Sources