Press Up(2), Down(2), Left, Right, Left, Right, B, A at the main menu. Note: Enabling this code will unlock the "Should Auld Acquaintance..." achievement, and will not prevent other achievements from being unlocked.
Successfully complete the game.
Complete the following achievements to unlock Xbox Live Gamerscore points.
Additionally there are nine secret achievements.
Enter the cemetery where Lady Comstock's mausoleum is located. Search the gravestones to the left of the entrance to her grave. One of the graves is features the handwritten word "SNIGHT", which is a reference to Mike Snight, a member of the development team.
Exit the gondola station and ride the Sky-Line for the first time. Ride the Sky-Line until you stop, then shoot the single soldier who is facing away. Reload the last checkpoint and repeat the process as many times as needed. Note: Headshots done while hanging from hooks will not qualify.
When you reach the Housewares areas of Fontaine's (after the Tram ride), find the shop front entrance called the "Bistro". This area has two levels. Go to the lower area at the bottom of the curved stairs to find some health packs on the right-hand side. There is a checkpoint here after all threats are gone. Walk behind the counter and use the code "3958" from the top down to access the storage area. Immediately equip the new "Radar Range" weapon and turn around to face a few targets. The actually number of targets varies according to the difficulty setting. Hold [Fire] at the target near the center of the group until one turns red and explodes. Both enemies in the blast radius will qualify towards "Chain Reaction". Reload the saved game from the checkpoint and repeat the process.
While progressing through the storyline, you will find pieces of gear that can be worn by the main character. There are four slots for them in your inventory, hat, shirt, pants and boots. Once you have all four items of each type, Equip them at the same time.
After getting the Ironsides Vigor at the start of Chapter 3, you will enter a duct system. You will eventually reach an exit with several enemies below. Kill them carefully, then drop out the vent and move to the left. There will be two more enemies near the bottom of the steps on top of the large Fink's cog symbol. This is a checkpoint. Inside the door are two enemies, one directly in front and one to the left behind the console. Draw the threat and use the Vigor. There are several bodies inside that typically have an Eve refill, allowing you to prolong this instance. When you run out of Eve, reload from the checkpoint and repeat the process.
When the first wave starts on Duke and Dimwit Theatre, jump on the rail moving counter-clockwise. As you go over the top of the enemies, they will fire rockets at you. Shoot them out of the air.
Use Peeping Tom and immediately activate your melee attack. You will rush towards the target slightly as you knock them out. If the warning markers appear above the target just as you act, it will not qualify. Immediately after you see the Big Daddy, go to the right into a room called "Test Drive". You will hit a checkpoint as soon as you walk past the sign in the middle of the room in front of the counter. Behind the counter is a single target that is perfect for this use because you can restart from the checkpoint each time.