Depending on what you do during the game you'll see one of four main endings, here's how to get them:
ApostleCorp Great Advance
Upload Aquinas Spec to JC Denton, use the machine at the base of the statue and keep JC Denton alive.
Illuminati Age of Light
Upload the Aquinas Spec to Illuminati, destroy the machine at base of statue, kill JC and Paul Denton and keep either or both Chad and Nicolette alive.
Omar Invasion
Don't upload the Aquinas Spec to anyone, destroy the machine at the base of the statue and kill the leaders of all factions.
The Templar Flood
Upload Aquinas Spec to the Templars, use the machine at the base of the statue, kill both JC and Paul Denton and keep Saman alive.
Assassin Pistol
This is a pistol with a zoom function instead of a flashlight, and also seems to be more powerful. It is a good substitute for a sniper rifle. It is inside the Nine Worlds Tavern in Trier Germany. Once inside, there is a part where you will see stairs that lead up to a closed door and down into a bar. Go up, pick the lock, and enter. You will meet the Omar here if you can find their contact. In one of the corners under some junk (you must throw it around as it hides the stash), you will find the weapon along with some other assorted items.
Dragon Tooth Sword
This is an energy sword that hurts very much. Go inside JC's sanctuary. It is on top of a bookshelf when you enter the first remembered area (Maggie Chow's apartment, Hong Kong, from the first game).
Emerald Suites Penthouse
At the Greasel Pit bar in Lower Seattle, you can talk to the man who owns the penthouse at Emerald Suites. Talk to him and agree to be his "chamber boy". He will give you the key. He warns you to stay in the kitchen "or the bot will take offense". However, it is just a spider bot and can be taken out easily. From there, you can hack the security terminal to turn off the laser grid, then go upstairs and hack another to open his vault. From in there, you can find all sorts of items , including an Energy Blade and the evidence the WTO wants you to find for a secondary mission.
Explosive crates
Use explosive crates whenever you can to blow up cameras, beams, turrets and almost anything else that gets in your way.
Free Biocanister
Find the mutant and get a sample before bartering with the Omar in Seattle to get a 50% discount and a free Black Market Biocanister. It is in the basement of Club Vox in Upper Seattle.
Free Pilot
You will need some Multitools and the Neural Interface Biomod to do this trick. In Lower Seattle, there is a bar called the Greasel Pit. Look around until you find an empty room with a Holocomm inside. A girl named Ava Johnson will start talking to you, saying that the WTO is holding her captive. She wants you to help her escape. Go to the WTO Air Terminal and to that elevator that two guards are standing by (you will have the keycode by now). Wait until the bot is not looking then move straight up the stairs. Go all the way down the walkway. To your right is a building guarded by a camera. Sneak past the camera and unlock the door with a Multitool. Go in, hack the security computer, turn off the turret, then sneak back up the walkway. To the left there is a bot guarding another building. When it is facing away from you, drop down and crouch behind the boxes or the turret. Wait for the correct moment to make a dash for the door. Once inside, deactivate the second turret, but do not leave just yet. There is a vent in the room that you can use a Multitool on. Hop in, move to the right, and get the other Multitool. Then, go back and head up the vent. You can turn on the Pilot Beacon from inside this room. Head back down the vent. There are now more guards outside looking for you. It is slightly difficult to get to the helipad from here, Try waiting until the bot is not looking and make a mad dash for it. Once you talk to Ava, she will give you free transportation for the rest of the game. It is difficult to do this, but is well worth it as you will have a lot more money to spend on other things. Note: If you are working for the WTO they will get mad at you for doing this, but will let it slide.
Funny Glitch
This glitch is to fit a npc into a bin or storage container you must first kill an enemy then pickup the body throw him into a container if you still have the baton you can do this now smack him until he fits then close the bin (Note: sometimes it wont work but it usally will) and just for fun throw a concussion mine (timed explosion) and just watch the explosion!
Getting items
When in any area, check dumpsters and look behind small boxes or items for multitools, food, guns, ammo, etc.
Have bot powers
Note: Save the game before doing this. Get the Bot Domination Biomod. It helps to upgrade it to level 3. Next, find a bot and attempt to dominate it. Find a door or entrance that leads into another zone via a loading screen. Let the timer count down and time your exit just as you are going into the bot's peripheral vision. The screen should stay white upon your exit. If you did not time it correctly, you will be booted to the Xbox menu. Now when you are in the area you exited to, all of your inventory items will be gone, but you will have the bot's weapon. Note: The Spiderbot's weapon is null and will not do any damage.
Hellfire Boltcaster
This is a boltcaster that makes enemies burst into flames instead of being knocked out. Its inside the Nassif greenhouse and is slightly difficult to get. Go through the warehouse and into the office, then make a left in the hall (away from hydroponics control). Then, save the game when you get to the balcony save (so you do not have to run all the way around). Carefully jump to the beams sticking out on the other side of the rail. Then, jump to the ledge to your right. It is small, but you can stand on it. Use the outcropping window as a foothold to jump up onto the balcony above you, then go through the vent shaft. In this room you will find the weapon in the corner amidst some junk.
There is a hidden Boltcaster in the Tarsus Academy in Seattle. Go to your room and Billie will tell you to look up at the ceiling. It will disappear. Then, jump and climb up onto the ledge above the counter. Jump to the other side and you will find a Boltcaster.
Mega-Jump
Position yourself a few feet from a low lying object (stairs [recommended], seat of a couch, non-movable bench, or others about the same height) and start running towards it. Just as soon as you start to walk over it, jump. You should jump 2-3x as high as usual.
More Candy/Soda
If you want more candy/pop when you are hacking the machine before you get done hacking repeatedly press the X button and when another hacking screen comes up you will hack it again and get more of that item. Note: Does not work with atms.
Proximity mines
You can use the alternate fire of the proximity mines to set a timer. This is also useful for blowing up beams and turrets that are not triggered regularly.
Red Greasel Hunter
This is a pistol with a red flashlight. In Lower Seattle, you can find this under the sewer grate in front of the Greasel Pit Bar. It is lying near or under an Omar corpse. Watch out; you will have to kill two Karkians to get it. If you do not like close encounters, once they start chasing you, climb out and drop a concussion grenade on them.
Save health and energy
Using the Active Black Market Biomod that allows you to control an EMP Armed Spybot next to an Engineering Bot that refills your Bioelectricity. This allows you to have an infinite range. You can destroy all electrical equipment and bots in the vicinity without having to use energy cells or risk health.
Seattle: Entering apartments
In the Emerald Suites in Seattle, there are several ways to enter the penthouse, Dr. Nassif's apartment, and apartment 2226 in which the lawyer who the owner of Club Vox asks you to kill, lives. If you have several Multitools, use them to disable the power in the elevator shaft. From there you can access a vent shaft that leads to the Minister Of Culture's penthouse. At the end of the hall (not the penthouse), you can find a Multitool under the staircase. Use it to disable the power to the alarms of apartment 2226 and you can break the glass sunroof to gain entry. You can also use the Glass Destabilizer and save your Multitool. However, be sure to have an EMP or Scrambler Grenade for a Security Bot on the roof. Elsewhere in the suites is an easy to find vent shaft that leads into Dr. Nassif's apartment.
Secret Party Level
On Liberty Island, go to the underground UNATCO Ruins and pick up the UN Flag in the office that has been destroyed, and then take it to James Manderley's office from the original title. Set the flag in the bathroom and flush the toilet to be transported to the Uber cool Secret Party Level.
Secret Weapons
Toxic Blade- Apt. 2225 Emerald Suites in upper seattle, under a pillow
Red Greasel Hunter- Lower Seattle Slums, in the sewer tunnel with 2 Greasels in it, under the dead omar, looks like a pistol
Assassin Pistol- Der Blutende Rabe Curio Shop in Germany
Widowmaker SMG- Maintenance room in the Nanoformer Programing tunnels of Arcology Level 107 in Cario, Egypt
Hellfire Boltcaster- Abandoned Apartment overlooking Nassif Greenhouse in the Cario Medina
Take out weapon on ladder
When you climb a ladder, you will automatically put away your weapon. Press B to take it out while still on the ladder.
Thief 3 preview
Successfully complete the game to unlock a preview of Thief 3 in the "Extras" option.
Toxic gas
Shoot cylinders that contain toxic gas to fill a the room and kill anyone within the blast radius. Also, if you have the strength modification you can pick up these cylinders and throw them into a desired room. This is a good way to kill guards without being seen.
Toxin Blade
This is a knife that does excellent damage and stuns your opponents with the first hit. In Upper Seattle within the Emerald Suites building, you can find the Toxin Blade. It is in the apartment next to Dr. Nassif's under the pillow on the bed. There is one hostile in the apartment.
Widowmaker
This is a SMG that fires Spider bots instead of flash grenades at the expense of an entire ammo clip. It can be found in the Cairo Archology on your second visit. From floor 107, near the Templar recruiting booth and Tarsus academy, go down the ramp into the maintenance area. Make a left and look on the right wall for an opening. Crawl in, make a left, then look left for another opening. Push the junk out of your way and enter the little hiding place. It is near a corpse.