Holo-drone
From Halopedia, the Halo wiki
Holo-drones are small, spherical objects capable of hovering and flying, that create holographic fields. Holo-drones are used in many ways by the Covenant. They can be used as communication devices or as holographic decoys of individuals.
Sesa 'Refumee, the leader of the Heretics, was fond of these and used them as decoys of himself when the Arbiter attacked the Heretics' Base.
They are very weak in battle as a direct shot can destroy them. They look like Plasma Bombs only bigger and they can hover.
