The Mongoose is a vehicle in the Halo series which makes its debut in Halo 3. Imagine the Warthog minus the usefulness, and you have the Mongoose.
It was sorta cool in some moments in the campaign of Halo 3, but after that and in the multiplayer, it's rather stupid. It has no defensive shielding, and there's no firepower for the driver. You can take on one passenger but it never works out they way you planned it. Just drive fast enough to a vehicle worth its weight.