Double Warthog driving glitch
From Halopedia, the Halo wiki
Through a glitch in Halo PC one player can control or "slave" one Warthog without a driver to follow an occupied Warthog.
Walkthrough
This is a very intresting glitch. First you park 2 Warthogs, front end parallel to the back end, side by side. Then you sit into both seats LOTS of times which makes the computer think that you are in both Warthogs. Kow here's the interesting part. Drive in one Warthog then the empty warthog will go to in the same direction.
