All Weapons:
During Gameplay press: right,left,up,down,A,up,X,A

God Mode:
During Gameplay press: right,left,up,down,A,right,left,black,white

Nail Gun:
During Gameplay press: right,left,up,down,A,white,white

Mega Force:
During Gameplay press: right,left,up,down,A,right,right

Hitman full health:
During Gameplay press: right,left,up,down,A,up,down

Toggle lethal charge:
During Gameplay press: right,left,up,down,A,black,black

Equip weapons:
During Gameplay press: right,left,up,down,A,up,right,right

Hitman Ali:
During Gameplay press: right,left,up,down,A,left,left

Hitman Ali:
During Gameplay press: right,left,up,down,A,up,up

Slomotion:
During Gameplay press: right,left,up,down,A,up,left

The Meeting:
If you're having trouble figuring out who you have to kill at the St.Petersbourgh stakeout what you should do is get to the building as quick as you can kill the guards out front silently. Then run up the stairs ,turn left if they are still in the room, kill the guy on the opposite side of the table. If they are running down the flight of stairs the first guy will be wearing a red leather jacket, kill the guy behind him and run as fast as you can to the train station without being killed.

All weapons:
On the title screen press XBAXBXA AND THEN PRESS LEFT TRIGGER

Get Silenced Ballers:
Get a Silent Assassin Rank in any mission

Get Sawed Off Shotgun:
Get a Silent Assassin Rank in any 2 missions