Finish the first level in under 20 seconds
This can be done in any difficulty. The first level (Courier) begins with 2 objectives: Collect equipment from the safety deposit box, and avoid civilian casualties. From the begining of the level, head toward the safety box, but before opening the box to get your stuff, punch, or stun (but do NOT kill) the security guard standing near the box. You will see a "mission failed" message on your screen, and Robinson will tell you to come back because the mission was compromised. Still, take the box, and walk away from the level. When you leave, you will still have completed the level. The reason for this is that if you harm, but do not kill the guard, new objectives stops appearing, so even though you "failed" the mission, the two initial objective (Take the box and do not kill civilian) are still sucessful, and thus, the game "thinks" that you suceeded in the mission.
Jump From High Distances and Live
If you want an advantage in this game then you need to use this trick. When you jump from a high distance, IE the top of a building in Skyrail, tap the Up-C button, or whatever button is your jump button, right before you hit the ground. You will hit the ground unharmed and be able to run away from people very easily.
Multiplayer Gadget War
To unlock the gadget war in multiplayer, you must finish the 'Fallen Angel' level on secret agent difficulty in 2:45 or less.
Air Raid Scenario
Beat the Masquerade level on "Agent" difficulty in under 3:15.
Capture the Briefcase level
Successfully complete the Turncoat single player level on the "Secret Agent" difficulty setting with a time less than 3:20 to unlock the Capture the Briefcase multi-player level.
Castle level
Successfully complete the Subway level on the "Agent" difficulty setting with a time less than 2:15 to unlock the Castle multi-player level.
Change Gun Options
Hold B and press Z to change options on your gun. For example, you can make the Wolfram P2K have a silencer. Note: Every gun does something different.
Civilian Skins
Successfully complete the City Of Walkways 1 level on the "Agent" difficulty setting with a time less than 3:35.
Classic Skins
Finish the game using Secret Agent difficulty to get new skins such as Odd Job, Scaramanga, Baron Semody, Jaws, Tuxedo Bond, and more.
Contemporary skins
Successfully complete the game on the "Agent" difficulty setting to unlock Alec Trevlyan (006), Wai Lin, Max Zorin, May Day, and Christmas Jones (dress).
Covert skins
Successfully complete the City Of Walkways level on the "Secret Agent" difficulty setting with a time less than 3:45.
Forest Level
Successfully complete the Night Watch single player level on the "00 Agent" difficulty setting with a time less than 2:20 to unlock the Forest multi-player level.
Forest Scenario
Successfully complete the Night Watch single player level on the "00 Agent" difficulty setting with a time less than 2:20 to unlock the Forest multi-player scenario.
Golden gun mode
Complete the game in 00agent to receive golden gun mode.
Health at 100%
In the mission where you chase the female assassin (mission 3) Thames Chase, when you are defusing the bomb, stop the clock on exactly 0.07 seconds left and your health will be topped back up to 100%.
Make your enemies surrender
To make your enemies surrender you must first find an enemy to work on. Once you have found an enemy, use the stuner on your watch to paralyze him. Stun the enemies from a medium distance until they drop the weapon they are holding. Than Quickly pull out a pistol or any non rapid firing weapon and shot them once in the foot. Stay close to the enemy or they will pull out a pistol and soot you. You can now do whateveryou want with them.
Navy Skins
To unlock Navy Skins in multiplayer,beat:A Sinking feeling on 00 agent in under 2:55
Scientist skins
Successfully complete the Masquerade level on the "00 Agent" difficulty setting with a time less than 4:20.
Sky Rail level
Successfully complete the Cold Reception level on the "Secret Agent" difficulty setting with a time less than 3:15 to unlock the Sky Rail multi-player level.
Soldier Skins
Successfully complete the Midnight Departure level on the "Agent" difficulty setting with a time less than 3:05 to unlock the Soldier Skins.
Suit Skins
Finish the Courier level with a time less than 2:00 using Secret Agent difficulty.
Unlock Skins
Finish the game using Agent difficulty to get new skins like May Day, Christmas Jones (Dress), Alec Trevlyan, Wai Lin, Max Zorin.