The Halo Cache Editor allows user to edit Halo maps directly on their Xbox.
With the use of a mod-chip, the Halo Cache Editor can be loaded through the hard drive onto the Xbox. The Cache Editor allows for such things as when on campaign to become a Hunter, Sentinel, Flood or even a Grunt. There is the use of the "Spiderman" mod which allows you to walk on ceilings, walls, and outside of barriers. With the Cache Editor, it can allow players to shoot grenades, rockets or even Scorpion shells from a pistol with the use of the "projectile" mod.
This tool is also very similar to the PC equivalent, HMT (Halo Mapping Tools).
The cache editor was used on the Xbox by many players to "walkthrough" campaign, and it was also used in Halo 2 multiplayer.
The program basically switches meta tags, like what HMT does to Halo PC. In order to run this program, you need to have a modded xbox, either softmodded or hardmodded.