The Bandana skull is perhaps the best in Halo Infinite. This skull unlocks infinite ammo for all of your weapons and grenades. It also removes all equipment cooldowns so you can use them repeatedly. Here is where you can find the Bandana skull in Halo Infinite.
The Bandana skull is located in the final level of Halo Infinite called Silent Auditorium. Once you reach this level, progress as normal until you find a room that Sentinels spawn in. In this room, you are allowed to kill the Banished enemies but avoid killing any of the Sentinels. Killing the Sentinels will cause the door that leads to the Bandana skull to lock.
After you exit that room, you shouldn’t have to worry about any more Sentinels. If they do spawn, avoid them and keep progressing through the level like normal until you reach a room with two doors and a long hallway. The door opposite of where you came in should be glowing blue. If not, you will need to restart the level. Go through the door and climb up on the platform in the center of the room to find the skull.