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<ref>Halo 2, level The Arbiter.
Sesa 'Refumee, the Elite leader of the Heretics, used them as decoys of himself when the Arbiter attacked the Heretics' Base<ref>Halo 2, level The Oracle.
They are very weak in battle as a direct shot can destroy them. They look like Plasma Grenades only bigger and they can hover.
