If you want to unlock some particular cheats e.g unlimited ammunition,unlimited health or more also the concept art you will have to finish the whole game for once.
Get Bonus On Game Completing
Completing the campaign mode will unlock the character, environmental in your additional menu list.
Dead-eye: Fifty points:
In normal to higher difficuly you have to finish any mission with atleast an accuracy of 80%.
Defender: twenty points:
Help in defending the barricade in New York on Higher or Normal difficulty.
Dolly Madison Award: twenty points):
Constitution must be saved from getting burned in fire on higher or normal difficulty.
Environmentalism: Fifteen points:
Complete 40 grapple kills or 40 environmental on any difficulty.
Clingy Twenty Five Points:
Kill/Finish 15 of the enemies in a row. You can do this by grappling them as they come on any difficulty.
Combat Veteran: 25 Points:
Just finish 250 of enemies in a campaign on any difficulty.
Compat Experience: Ten points:
Finish all 50 enemies in a campaign on any difficulty you get.
Exploding Monkey Twenty Points:
Make one explosion and kill at least 4 rivals, you can do this on any difficulty.
Going Nuclear Thirty Points:
Rewire an Atom Bomb on Normal or Higher difficulty. Rewire an atomic bomb or higher or normal.
Gravity is a Harsh Mistress: Five points:
Tossing the paratrooper onto the streets below the New York on any Difficulty.