Colour me surprised, especially since I played through the game twice and didn't notice him, but the Master Chief does appear to make a quick cameo in the end of Halo: Reach.
Be warned if you don't want the game SPOILED for you, don't watch the above video.
If you don't care, press play and be delighted. I checked with some sources in the know who seem to think this is a legitimate Easter Egg. Well played, Bungie. And great find Achievement Hunters.
Halo Reach: Master Chief is in Reach "Easter Egg" [Achievement Hunter]