Scarab

The Type-47 Ultra Heavy Assault Platform, more commonly known as the Scarab, is a Covenant mining vehicle adapted for use in combat.

Introduction
Developed in an advanced construction site, Scarabs are mobile fortresses. The quadrupedal behemoths are typically deployed from low- or medium orbit, or from high atmosphere. They are used to attack heavily-defended structures, and often lend quick but unstoppable support to Covenant troops on the ground. Scarabs are extremely powerful, possessing an exceptionally powerful plasma beam (mounted onto its "head") as well as one or two dorsally-mounted anti-air cannons. Their "bodies" are massive and multi-level, and they possess four or six legs (depending on model). Unlike most Covenant vehicles, Scarabs do not use anti-gravity propulsion to move. Scarabs instead walk using their massive legs, which are surprisingly swift and and precise given their size. The legs can also be used to crush enemy forces on the ground. It is thought that some amount of anti-gravity propulsion is used to reduce stresses on the legs.

Pictures
http://images3.wikia.nocookie.net/halo/images/thumb/c/cd/Scarab.jpg/300px-Scarab.jpg