Wow, what happened. Half the stuff in that trailer didn't make it into the game. Energy sword, wildlife, a revanant, elites with a hand shield. Not to mention that whole scripted sequence never existed in the final cut.
My sarcastic tone doesn't translate over the Internet, which makes me sound like an ass. Usually I mean no offense.
Technically that isn't Halo. That was one of the Beta builds for the Macintosh that Bungie was initially planning on. Once Microsoft bought them, they wanted an FPS not an RTS, and a year to do it. So lots of assets dropped, for the better.