Level skip with Silent Assassin rank and special weapons:
Press R, L, Up, Down, X, A , click Left-Analog stick, press
B, A, B, A during game play when a level first starts.
Press X, Y, B, Left, Up, Right, L, R at the main menu.
When you are killed, the screen will turn black and white briefly.
Try to shoot four people in the head while this is happening to
resume playing with barely any health.
Successfully complete the indicated mission with a "Silent Assassin"
rank to unlock the corresponding weapon.
CZ 2000 Dual Pistols: Mission 1
Micro Uzi Dual Submachine Guns: Mission 2
Silverballer Silenced Dual Pistols: Mission 3
Magnum 500 Dual Pistols: Mission 4
Sawed-Off Shotgun Dual: Mission 5
M4 Carbine Silenced Assault Rifle: Mission 6
SG220 .S Dual Pistols: Mission 7
MP5 Silenced Submachine Gun: Mission 8
AK 74 Silenced Assault Rifle: Mission 9
GK 17 Dual Pistols: Mission 10
Micro Uzi Silenced Dual Submachine Guns: Mission 11
PGM Silenced Sniper Rifle: Mission 12
All weapons in training level:
Start the training level, then enable the "Level skip" code. You
will complete it with a "Silent Assassin" rank. Choose the training
level again, and all the weapons in the game will be unlocked in the
weapons storage area. This also will unlock the Cardboard Tube weapon.