X-Men: The Official Game Cheats
Street alternate costume
By collecting all Weapon X files with a character you will unlock his or her alternate street costume.
Comic alternate costume
By collecting all Sentinal Techs with a character you will unlock his or her alternate comic costume.
Danger Room missions
Progress through the game to unlock the first three Danger Room missions. Six more Danger Room missions are unlocked by collecting all Sentinel files and Weapon X files with all characters.
Finding Tech Pieces
To save time and frustration, run through the level on novice to find all six Tech Pieces, then distribute mutation and save the game. Go back on the higher levels to gain the missing mutations, without worrying about racing around trying to find the pieces (especially on timed missions).