Floating Hat

In the Halo 2 level Cairo Station after the cinematic rolls, as you descend on the stairwell, you will turn and there will be several SMG's and Battle Rifles. Adjacent to this, is a crate where an officer has left their cap. Melee the crate with the Naval Officers cap on it repeatedly. The crate will eventually slip from under the hat, and the hat will be there, motionless. You can't do anything else with it. It's just a minor programming error by Bungie.