On the PDA's faction screen, enter UP, DOWN, UP, DOWN, LEFT, RIGHT, LEFT, RIGHT on the D-Pad. You should hear a click that signifies the code is active. The merc will be invulnerable to all sources of damage (you may have to Medivac if you fall into deep water). This also applies to the current vehicle the merc happens to be operating at the time.

Mercenaries Cheat: Infinite Ammunition
Note: Use this cheat with care, as the possibility of it altering your save file exists.
Go to the PDA's faction status screen and enter the following on the D-pad: RIGHT, LEFT, RIGHT, RIGHT, LEFT, RIGHT, LEFT, LEFT. A soft click should confirm the code's activation.

Mercenaries Cheat: Add $1,000,000
Go to the PDA's faction status screen and enter the following on the D-pad: RIGHT, DOWN, LEFT, UP, UP, LEFT, DOWN, RIGHT. A soft click should confirm the code's activation.

Mercenaries Cheat Ghost Mode
Ghost Mode ... UP, UP, DOWN, LEFT, RIGHT, UP, LEFT, DOWN, RIGHT, UP, LEFT.

Mercenaries Cheat Unlock Hidden Cheats
On the PDA faction screen input the following codes:

Enable All Locked Cheats ... RIGHT, RIGHT, LEFT, LEFT, UP, UP, DOWN, DOWN, UP, RIGHT, LEFT, DOWN, DOWN, LEFT, RIGHT, UP, DOWN, DOWN, UP, UP, LEFT, LEFT, RIGHT, RIGHT.

Enables the following "locked" cheats to work:

Random Skin ... UP, DOWN, UP, RIGHT, DOWN, LEFT, UP, LEFT, RIGHT, RIGHT, LEFT, DOWN.
Skin - A.N. Pilot ... LEFT, LEFT, RIGHT, RIGHT, UP, DOWN, UP, DOWN.
Skin - A.N. Pilot (no helmet) ... LEFT, DOWN, RIGHT, DOWN, UP, UP, RIGHT, LEFT, DOWN, DOWN, UP.
Skin - Hearts ... LEFT, LEFT, RIGHT, RIGHT, UP, DOWN, DOWN, UP.
Skin - Spades ... LEFT, LEFT, RIGHT, RIGHT, DOWN, UP, UP, DOWN.
Skin - Doctor/Diamonds ... LEFT, LEFT, RIGHT, RIGHT, DOWN, UP, DOWN, DOWN.
Skin - Ace of Diamonds ... LEFT, LEFT, RIGHT, RIGHT, DOWN, DOWN, UP, UP
Skin - Buford ... LEFT, LEFT, RIGHT, RIGHT, UP, DOWN, DOWN, DOWN.
Skin - Garrett ... LEFT, LEFT, RIGHT, RIGHT, UP, DOWN, DOWN.
Skin - Joseph ... LEFT, LEFT, RIGHT, RIGHT, DOWN, UP, UP, UP.
Skin - Colonel Peng ... LEFT, LEFT, RIGHT, RIGHT, UP, DOWN, DOWN, LEFT.
Skin - Han Solo ... LEFT, LEFT, RIGHT, RIGHT, UP, DOWN, UP, UP.
Skin - Indiana Jones ... LEFT, LEFT, RIGHT, RIGHT, UP, DOWN, UP, UP.
Skin - Mafia ... LEFT, LEFT, RIGHT, RIGHT, DOWN, UP, DOWN, UP.
Skin - DPRK Elite ... LEFT, LEFT, RIGHT, RIGHT, DOWN, DOWN, DOWN.
Skin - Civilian ... LEFT, LEFT, RIGHT, RIGHT, DOWN, DOWN, DOWN, DOWN.
Skin - ROK Elite ... LEFT, LEFT, RIGHT, RIGHT, DOWN, DOWN, UP, DOWN.

Mercenaries Unlockable: Playground of Destruction
Beat the game to unlock Playground of Destruction mode. You will have all of the cash and items you earned in the previous game.

Mercenaries Unlockable: Blueprint Rewards
1: All C4 crate supply drop
5: Sniper Rifle Supply Drop
10: Stinger Supply Drop:
15: Anti-Tank Rocket Supply Drop
40: Prototype Rifle Supply Drop
60: $100,000
70: $100,000
80: $250,000
90: 250,000
100: 500,000

Mercenaries Cheat: Reset Faction Status
Head for the faction status screen of the PDA and enter UP, UP, UP, UP, DOWN, DOWN, RIGHT, LEFT. This resets all faction meters to neutral (yellow) and sets the Allied Nations as friendly (green). Note this will affect the prices in the Merchant of Menace if your status with the Russians is not neutral.

Mercenaries Hint: Free Vehicle Repair
Did you hijack a rare vehicle (i.e., a helicoptor gunship) and want to keep it for a while? Go to any faction HQ and make sure that the last vehicle you entered and exitted is the vehicle you want to keep (and have repaired). Accept the contract. Once the merc is outside the HQ once more, locate your parked vehicle and cancel the contract. Decline to retry the contract and your vehicle will be available with full and ammo.

Mercenaries Hint: Chopper Ride At Kirin-Do
After the cutscene of your character landing on Kirin-Do, quickly turn around and hijack the Transport Chopper. Though it isn't shielded from radiation, it makes getting to the Type-07 prototype and General Chang a lot easier.

Mercenaries Hint: Free Mi-17 Chopper
If you just need a reliably consistent (always there) chopper in the north province, try the Mafia HQ. Next to the garage there should ba a man with a dollar sign for a challenge. Go accept the challenge and fail it by leaving the chopper. Once you do, you may claim the heli normally and go about your own business.

Mercenaries Glitch: Faster Beacon Timers
You can glitch the beacon timer by purchasing the same item in the Merchant of Menace shop once the first beacon is deployed (this assumes you have access to that same item in the Mafia shop). Just beware that the maximum number of shop choppers delivering supplies is one; however, this glitch allows you to call in one chopper right after the previous with little delay.

Mercenaries Hint: Chopper Locations
South Province:

• UH60 Transport - The $ Challenge southwest of the DMZ (the AN HQ is in the DMZ area on the map).

• UH60 Transport - Northeast of the DMZ. This chopper becomes available after the Ace Of Clubs contract is resolved successfully.

• LHX Chopper - Inchon. This chopper is available after the South Korean mission involving the missile trucks at Inchon is resolved successfully.

• WZ-9 Chopper - Pyongyang Airport. This chopper is available after the Chinese mission involving Nampo is resolved successfully.

• NK Transport - North of Changsong Train station's eliptical road there is a small rise next to the restricted airspace with a ZSU and a chopper on it.

• NK Gunship - East of Changsong Train station there is an eliptical road. Head east from it and a small airbase can be found with several gunships and SAM carriers.

• Coaxial Gunship - This is a unique chopper that can only be found during the second Russian mission while verifying the Spades. The temple northwest of the Industrial Zone has the chopper, along with one of the mission's objectives.

• AN Gunship - This takes a little work. You also need a sniper rifle. Head to the east entrance of the Kusong MASH and climb the surrounding hills. A random set of gunships and transport choppers hover over the MASH (if you do not see a gunship, you can save/load your game). Snipe the pilot of a gunship as it passes over the MASH; the resulting accident will usually leave the gunship in barely flyable condition, and cost you $25,000 (for killing the AN pilot).