From Halopedia, the Halo wiki

A fan-made image of Mister Chief created for use in Template:Realworld.
This article contains information about a non-canonical subject that, while official, is not part of the established Halo universe.
The "Hummer."

The "Hummer" (officially designated in the RTS build as "scoutcar") was an early version of the Warthog, designed and discarded by Bungie. It was used in an early 100 polygon build of Halo: Combat Evolved based on their previous game Myth.[1] It was based on the real world Humvee/HMMWV and featured a pair of roof-mounted machine guns.