In the last part of Halo 2 on the level The Great Journey during the Boss Fight with the Brute Tartarus, it is possible to Fight Tartarus with a Banshee. This may take a few tries to get on approach and takes a great deal of patience, but is well worth it to certain players.
Instructions
In the second to last part of the level where Sergeant Avery Johnson destroys the door with a Scarab, wait for him to shoot the door then fly into it. Though not required, it is advisable that you destroy the two wings of the Banshee before you enter the door. You can still make it with the wings, but you'll just damage them and it will take a longer time. After you get inside the door, start flying upward and then forward. You will fly over one wall and then get stuck in between two walls. When this happens, fly downward. Your Banshee will end up in front of the door.
At this point, get out of your Banshee, so the door will open. Do not get back in the banshee yet. A few Brutes will engage you, posiably destroying the banshee if you brought it in the room. After they are dead, get back in the Banshee and fly in the room and through the doors the Brutes came in. When you do this, a cutscene will show Tartarus activating Delta Halo. After the scene finishes, you can either kill the Brutes and then run backwards past Johnson, or just get the banshee right then when the scene ends. Your Banshee will be sitting in the hallway of which you can go into and fly through the pillars to fight Tartarus.
Tartarus will try to attck you, but a few Fuel Rod Gun shots should finish him. This can be an extremely good method to use on Heroic and Legendary difficulty settings for new and unexperienced players. Also, you can simply run him over and push him off the edge of the structure, instantly killing him.
After killing the Brute, the cutscene will play as usual, meaning this trick has no effect on the scene.