Leviathan Mobile Firebase
From Halopedia, the Halo wiki
The Leviathan Mobile Firebase is a UNSC vehicle cut from the development of Halo Wars. The vehicle is similar in size to the M510 Mammoth, being many times the size of an M12 Warthog and serving as a mobile Firebase. The vehicle is seen to have several different configurations such as a "Suicide assault" variant with nose-mounted saw blades and a "Paris gun" variant equipped with a massive artillery cannon. However, the primary variant appears to be a vehicle that would fill a role similar to that fulfilled by the M312 Elephant in the final game, sporting numerous machine gun turrets, a mobile barracks and the ability to tow a Shaw-Fujikawa Translight Engine, like that seen in the mission Reactor.