Holotank
From Halopedia, the Halo wiki
Summary
Holotanks are small devices widely used in the UNSC. They are used project a hologram of information, and are normally reserved for AIs, though other information can be displayed, such as mission recordings and holo-vids.
Images
http://img175.exs.cx/img175/4515/holotankthumb4id.jpg
