Successfully complete the game to unlock the "Enable Full Equipment" option at the "Extras" menu (for infinite ammunition, infinite items, etc.), and additional character skins.
The Displace suit is in the room next to the room where you have your last chance to save; the code is "5800". There are a total of nine suits.
When you must steal millions of dollars by using the lockpick, go to the small vault left of the computer. Use the lockpick, and the costume will fall out.
Find the wrench in the bathroom. The costume is in the room that is shaped like a "U", and has two cameras and four lasers. There is a keycard room in there. Once you enter the keycard room, in the right corner is a guard standing in the dark. Take him out and climb on the crate. Then, turn towards the next crate and select the option "Bash Door"; the costume will be in there.
Go to floor 3. To learn what door has the costume, look through the optic cable. Once you see the green package, enter the room; the keypad lock code to the door is "5800".
Before you try to find the costume, locate the wrench that is laying on the ground. Then, proceed through the level until you reach the man who is shooting from the top of the building. Once you kill him, get to where he was. Then, run across the rooftop to the vent. Exit the room you fall into. If done correctly, the icon "Bash Door" should appear in the top left corner of the room. Bash the door and the costume will be in there.
Once you go down to the elevator shaft Sam will consider the Descent to Hell. There will be lasers at the bottom. Once you are down there find a ladder to get back up. Once you climb it, you will end up in a small room with lasers. The costume is somewhere in the back corner.
Finish sniping the man on the roof, then before you rappel down off the platform, stay on the platform. In the high right corner is the costume.
When you cut the power and the guard is still alive, he will come to turn the power back on. Run past him as he comes through the doorway and he will say " Is someone there?". Run through the room. When you come back, you will find out that the lights are off and the guard is gone. He is around the corner. Take out your rifle and kill him. With most guards, when they say "Is someone there?", they stand perfectly still and you can shoot them easily.
Find someone underneath one of the poles that you can climb. Climb onto the pole and hook your legs up by pressing X. Make sure that your head is pointing towards person, then climb towards them. If done correctly, the interaction box should appear with the "Break Neck hit Y" message. Sam will hang down from his knees and break their neck. If this does not work, you can drop behind the person and grab them. Also, while you are hanging from a pipe with your legs down, press R and you will draw your 5-7 pistol. If you want to break someone's neck from a pole and they are walking about, put your legs down and draw your pistol. Then, shoot just ahead of them. They will say something like "Is someone there?" and come towards you. Put your pistol away and quickly press X. Note: You may have to press X twice. Wait for the man to walk underneath and you can break his neck.
You will reach a hallway after you fall out of a vent. There are three rooms in this hallway that require the lockpick to enter. In the third room will be a closet, just like the other ones; however this closet cannot be opened yet. Proceed to the bar, then go on stage and use the microphone. Sam will say something dumb. After he is done, turn around and look behind. A keycard should be somewhere. This keycard opens the previously inaccessible closet. Make your way back to this room and use the keycard to open the closet; the costume is inside the closet.
Go to the open area just before you enter the penthouse. Kill the two guards and climb the pipe at one of the ends of the area. From there, go left and jump down to the next platform. The costume should be somewhere around the corner.
Go to Zherkezhi's apartment and make your way to the first room on the top floor. Take out the guard and go to the long dark hallway at the top left of the room. There is a keypad lock to get in; the keypad code is "5698".
If you are on a mission where you cannot kill someone (for example, Manhattan Streets) take out your rifle from your back and equip it with a camera. Then, zoom in on the person's head. Shoot them with the camera, and make sure that it is the head or it will not knock the person out.