It's Master Chi-... Wait a minute. Something's off here. Fileshare Link: http://www.bungie.net/Stats/Reach/FileDetails.aspx?fid=3610861&player=CombatGam3r
That's an easter egg on the last level "Lone Wolf". What you do is play the map and into the cutscene for like 15 seconds, exit and go to theatre, play a little of it and press the back button. Once you do press B and then Y and Y again, you can float around, just go straight ahead and it's on the big thing there. Probably for another cutscene. Anyway, it's kinda cool. Shame it isn't rendered.