While playing a game enter: R2, L2, UP, Down, Cross, Up, Square, Cross.
Enter this code while playing a game: R2, L2, Up, Down, Cross, R2, L2, R1, L1.
At main menu, enter this code: R2, L2, Up, Down, Square, Triangle, Circle.
Beat any two missions with a Silent Assassin ranking.
Earn a Silent Assassin ranking on any mission.
Earn a Silent Assasin ranking on the St. Petersburg missions. Once you complete "Invitation to a Party," you unlock the M4.
