To enable the cheat mode, open the file "hitmanbloodmoney.ini" in your text editor and add the "EnableCheats" line to the end. Now you can press C while gameplay to call the window where you can enter cheat codes. You should press UP or DOWN and ENTER to enable the option. Note that 1 enables cheat mode while 0 disables it.
Invisible Mode: Invisibility
God Mode: God mode
InfAmmo: Unlimited ammunition
InfClip: Unlimited ammunition
Test Cloth: Cycle through disguises in current level
Complete level: To complete all objectives in current level
Time Multiplier: Speed up time where "10" is the highest value
Teleport: Teleport through levels
Beam here: Teleport to any location