Halo: Combat Evolved Anniversary skulls
From Halopedia, the Halo wiki
These will be game-modifiers with the appearance of a human skull that will be featured in Halo: Combat Evolved Anniversary.
Grunt Funeral Skull
Once the skull has been activated, every Grunt’s methane tank will explode like a plasma grenade when killed.
Trivia
- It is currently unknown wheather you will have to collect these skulls or if they will be unlocked from the start, like in Halo 3: ODST and Halo: Reach.