Unlock the following modes by performing the corresponding tasks:
MODE - HOW TO UNLOCK
Classic mode - Complete Campaign mode.
Hardcore mode - Complete Campaign mode.
Retro mode - Complete the game under the Hardcore mode setting. You can now toggle Retro mode from the "Options" menu to add a retro pixel filter to the graphics.
New Game + mode - Complete the game
Unlock the Devil Horns weapon by completing Classic mode. While using this weapon, Isaac will hold up the devil horns sign on his fingers when he is not shooting enemies.
C.M.S. Greeley side mission:
After you clear out the ship, you will reach the end of the objective marker in a room with the gravity panels on either side, with a discharging electrical transformer. Collect the Electro Shot mod to access the terminal in the final room. There is also a circuit behind the door that requires a wrench.
To get the N7 armor from the Mass Effect series, have a saved game file from Mass Effect 3.
New Game+ Unlockables:
In NG+ you can start a new playthrough with your previously earned inventory and resources. You can also access the Dead Space Legends Suit Set (Engineering RIG DS2 model) at Suit Kiosk. There are also abundant MK-II Overclocked parts and +3 circuits. Unlock the following items in NG+ by performing the corresponding tasks:
UNLOCKABLE - HOW TO UNLOCK
+3 Clip circuit set - Complete the game on casual difficulty.
+3 damage circuit set - Complete the game on impossible difficulty
+3 reload circuit set - Complete the game on normal difficulty
+3 speed circuit set - Complete the game on hard difficulty
Builder's Circuit Set - Collect all 12 Blueprints
Comms Circuit Set - Collect all 36 Audio Logs
Crafter's Circuit Set & Deep Dig Suit - Collect all 73 Weapon parts
Devil Horns - Complete Classic mode in New Game+
Devil's Horns - Complete the game on classic mode.
Earthgov, Unitology, S.C.A.F., and Alien Circuit Sets - Collect all of the specific set of artifacts
Engineering Suit - Complete the game on any difficulty
Flight Suit - Collect all 40 artifacts
Hostile Enviornment Suit - Finish all 10 optional missions in co-op mode
Mega Resources Deposit - Complete Pure Survival mode in New Game+
Mk-II Overclock Parts Set - Complete Pure Survival mode in New Game+
Mk-II Overclocked Attachment Set - Collect all 61 Circuits
MK-II Overclocked Frame Set - Complete all 10 optional missions
MK-II Overclocked Module Set - Collect all 71 logs
Mk-II Overclocked Tip Set & flight Suit - Collect all 40 artifacts
Research Circuit Set - Collect all 35 Text Logs
Retro Mode - Complete Hardcore mode in New Game+
Planet Cracker Plasma Cutter:
To obtain the Planet Cracker Plasma Cutter at the first workbench, have a saved game file from Dead Space 2.
Take the first letter of each chapter and arrange them in order to spell out the message "Brother moons are awake".
Unlimited items hints:
Get to the area near the end of Chapter 8 and look for a small building that must be entered by side-stepping a corrugated metal fence. The correct building has a generator to the right, bunk beds to the left, and an exit door ahead. While inside, leave the room through the door ahead of the beds. Oncethe door closes, turn around and re-enter the room. A random item will appear near the beds. Exit the room from the same door, wait for the door to close, then re-enter to repeat the process. The items are random and cannot be sold or crafted. -After reaching the end of Chapter 13 and defeating the Boss, an auto-save icon will appear while you move into a large snowy field scattered with crates. Do not continue to the exit. Instead, collect the tungsten and items from the crates. After that, pause game play and select the "Save And Quit" option to return to the main menu. Once done, select the "Continue From Last Save" option to return to the start of the snowy field area. The items in the crates will have respawned and can be collected again as many times as desired.
Get On My Level - Complete the game on any difficulty setting.
The Explorer - Complete all optional missions.
Gun Collector - Collect all Weapon Parts.
The Professor - Collect all Artifacts.
The Librarian - Collect all Logs.
The Armorer - Collect all Circuits.
My Buddy - Retrieve Resources from a Scavenger Bot at a Bench.
Metal Detector - Successfully deploy Scavenger Bots to 15 Resource Areas.
Strapped - Craft a Weapon.
Circuit's Edge - Add a Circuit to a Weapon.
EMT - Craft a Large Med Pack.
Full House - Craft a Weapon with 2 Tools, Tips, and Attachments with all Circuit slots filled.
Master Plan - Create a Blueprint that needs at least 2000 resources worth of parts and Circuits to build.
From the Jaws - Save your Co-Op partner from an execution by killing the attacker.
Share and Share Alike - Use the RIG to give an item to your Co-Op partner.
Medic! - Revive your Co-Op partner 10 times.
Architect - Share a Blueprint with your Co-Op partner.
Axes High - Kill 30 enemies using Fodder axes.
Payback - Kill a Soldier by TK'ing a grenade or rocket back at them.
Go for the Limbs! - Dismember 500 limbs from living enemies.
And Then We Doubled It! - Dismember 1000 limbs from living enemies.
Slow Mo - Kill 50 enemies while they are in stasis.
Blast Corps - Kill 30 enemies with explosion damage.
Shootbang - Kill 30 Soldiers with head shots.
Empty Chamber - Kill 30 enemies using melee strikes or a melee Weapon Part.
Dropping Acid - Dissolve 50 enemies with acid.
Electric Lawnmower - Kill 30 enemies using an electrified Ripper blade.
Overpowered Healing - Use quick heal to heal yourself 20 times.
Stranger in a Strange Land - Complete the Prologue.
Space Odyssey - Survive your first spacewalk.
Critical Mass - Recover the shuttle.
Snow Crash - Reach Tau Volantis.
Hydra - Kill the Snowbeast.
Together as One - Reassemble Rosetta.
Infernal Machine - Reach the Alien Machine.
Under a Buck - Shoot the deer head trophy in the Admiral's Quarters.
Space Ace - Shoot at least 70 targets during the ride to Tau Volantis.
Hungry - Reach the pump room of the Waystation without alerting any Feeders.
Drill Sergeant - Complete the Drill Room without taking any damage.
Aliens - Collect all Alien Artifacts.
Close Encounter - Kill 10 alien Necromorphs.
Epic Tier 4 Engineer - Complete the game in Classic Mode.
Survivalist - Complete the game in Pure Survival Mode.
There's Always Peng! - Find Peng.
RIG Master - Fully upgrade your RIG.
Ghosts of the Past - Face all of Carver’s demons by completing all Co-Op only optional missions.
Intestinal Fortitude - Defeat the Hive Mind.
Weedkiller - Kill 5 Cysts in the Biology Building with a single poison gas cloud.
Aren't You Thankful? - Complete the game on Hardcore Mode.
Shoot for the Moon - Defeat the Moon.
Brave New World - Earn all Bronze, Silver, and Gold trophies.
Heaven Can Wait - Awakened: Stasis your Co-Op partner when he is downed to slow his bleed out timer.
Heretic - Awakened: Kill the Unitologist Cult Leader.
Supercharger - Awakened: Finish charging the reactor in under 90 seconds.
True Believer - Awakened: Allow the Unitologist Cult Leader to survive.
Bad Moon Rising - Complete Dead Space™ 3 Awakened.
Get to the Chopper! - Awakened: Escape from Tau Volantis to the Terra Nova.
Just the Tip - Awakened: Craft a weapon using a MK-II Weapon Tip.
Pure Lunacy - Complete Dead Space™ 3 Awakened in Pure Survival Mode.