I was playing recently on COD Black Ops and came across a hacker. The players avatar was invisible in game (on friendly and enemy team) apart from the gamer tag which floated overhead if you were aiming at him. As far as I could see it was impossible to damage the guy even though hit markers did show.
I have reported him as you usually would do through xbox live but as I have irrefutable proof on video I would like it looked at by someone who can actually do something about it.
In respect of forum rules I have not uploaded the video or named and shamed