Infected Brute Chieftain

The Flood Brute Chieftain is a possible variant glitch of the Half-Infected Brutes Glitch that can be found on the Halo 3 level, The Covenant.

Walkthrough
It can be done by getting a Flood Infection Form to infect a Brute Chieftain. These two do not normally exist in the same area, although there is a War Chieftain at the third tower; however, the player must do a loading glitch and the time travel glitch, preferably on Co-op. The only way to get them together is to kill all your allies outside the third tower in the level, while leaving one or two Flood Carrier Forms alive. Kill the Carriers and let the Infection Forms chase you up into the snow area. Kill the War Chieftain stationed there and let the Flood take him over.

As observed in this video, after being infected, the Chieftain's appearance does not change except for some signs of Flood infection on his back. He retains all his normal combat abilities, including vehicle boarding. His shields stay down. The infected Chieftain attacks both the player and nearby Covenant, indicating that the Chieftain is allied with the Flood, contrary to popular belief.

Explanation
The infected Brute Chieftain may be an older version of Flood Combat Forms created in-game. The Flood would not totally change the host's body immediately after infection. This idea would have been cut from the game, possibly because the Combat Forms looked too similar to the original enemy.