Grand Theft Auto 4 (GTA 4)
[Edited by wolverinealaa, 7/18/2009 11:57:57 PM]
Because this game was one of the hardest games to train. It used XLive which made it impossible to do code-injection which got thwarted easily. However Caliber managed to do it, so as so much of efforts were put to it, CH decided not to release it in public.
However you can just google it for outside trainers.