Open the hitmancontracts.ini file it's in the folder where the Hitman game files are and add the following lines to it:
ENABLECONSOLE 1
ENABLECHEATS 1
Start the game and during gameplay press SHIFT ESC. Change the cheat value from 0 false to 1 true to enable the cheat.
God 1 :Enables God ModeGod 0 deactivates it
Giveall :Gives all weapons and items
Infammo :Gives Infinite Ammo for all guns
Nailgun 1 :Enables Nail gun Nail gun 0 disables
Invisible 1 :Makes you invisible to enemies
Invisible 0 :Deactivates invisibility
Finish Mission 9 with the silent assassin rating.
Complete Mission 1 with a silent assassin rating.
Finish Mission 10 with the silent assassin rating.
Finish mission 6 with silent assassin rating.
Finish Mission 4 with a silent assassin rating.
Complete Mission 2 with a silent assassin rating.
Finish mission 11 with the silent assassin rating.
Complete Mission 8 with the silent assassin rating.
Finish mission 12 with the silent assassin rating.
Complete Mission 5 with silent assassin rating.
Finish Mission 7 with the silent assassin rating.
Complete Mission 3 with a silent assassin rating.
When your health bar reaches zero the game will enter a black and white death sequence. If you are able to get four consecutive head shots on four different enemies during this sequence you will receive a small amount of health and return to the game.
On the level "Deadly Cargo," it is possible to get the M60. If you don't get it here, you will have to wait until the 2nd to last level. Make your way to where the SWAT sniper is, on the building overlooking the ship. After the SWAT team attacks the ship, a helicopter will begin circling the area. If you shoot the gunner on the ship, he will fall to the ground with his M60. Make sure that you assassinate the target first and you kill the gunner while the helicopter is over a land area that you can reach.
In the level Traditions of the Trade when you are on the 3rd floor you will eventually see a vacuum boy. When he opens a door to vacuum the room, go to the door and pick up the master key. You should then have access to most doors.
When playing The Meat King's Party look at the loading screen of the slaughter house. You should see a faint skull. This skull is also on the pinball machines in Rotterdam Rendezvous.
In the level Asylum Aftermath, once you get the double Desert Eagles, keep going forward through the second set of doors until you get to the last tank with a body in it, then look to the right and there is a tank with Lee Hong written on it.