These codes don't need to be entered in the console. Use a text editor, open up the file: hitmancontracts.ini. Insert 'EnableCheats 1' and save. Afterwards, start the game and the cheats during any mission. Also note that Case Sensitivity does matter. 

Password       Effect
IOIER          Bomb
IOIHITALI      Boxing Mode
IOIHITLEIF     Full Health
IOIRULEZ       God Mode
IOIGRV         Gravity Mode
IOILEPOW       Lethal Charge
IOIPOWER       Mega Force Mode
IOINGUN        Nail Gun Mode
IOISLO         Slow Motion
IOIPENNY       Unknown