From Halopedia, the Halo wiki
The Mongoose is the name given to a series of ultra-light all-terrain utility vehicles employed by several human organisations. It is popular in both the Civilian market and within the United Nations Space Command. The Mongoose is produced by AMG Transport Dynamics and has been in service since 2483. Both the civilian and military versions are available with a variety of upgrade packages, including armored body panels, improved suspension systems, and alternate engines. The civilian version is not rated to carry Spartans without risking damage to the frame.
The Mongoose provides an alternate means of transporting messages, documents, and light cargo between units. It may also be used to transport forward observers, reconnaissance personnel and sniper teams. Its proven versatility has made it a vital asset to field commanders when used as an alternate means of communication. The Mongoose seats one driver and sports a rear cargo rack which can carry weapons, equipment and, if the stirrup tracks are engaged, a passenger. In this configuration, the passenger can fire a weapon from the rear of the M274, effectively arming the vehicle. Field observations have indicated that when two Spartans are operating a Mongoose in this way, it becomes truly formidable, eclipsing its role of basic transportation and becoming something more akin to a force application vehicle.
The M274R Mongoose is another variant of the Mongoose platform, seemingly more widely employed than the M274. It was used by UNSC Army forces during the Fall of Reach. By 2557 it was still in service, seeing use in the Battle of Requiem and the later Requiem Campaign.
The M290-M Gungoose is the M290's weaponised platform, armed with twin grenade launchers.
Non-canon and dubious canon appearances
Mongooses are used by humanity for transportation.
List of appearances