lol I know some of you have seen something similar from the gameplay trailer, but this is from the live action trailer! And yes, I was the one who took the screenshot and added the text.
This is another screenshot I took from the new Halo 4 Live Action trailer: [link]
Here, we have Master Chief (bottom right) face to face with another Promethean Knight. Damn this shit looks awesome, still can't wait for its release!