Update: I was unfortunately not aware of Shamus Young's severe criticism of Fallout 3 available here to link in the original piece and I regret that. It dovetails rather nicely with what I've written and it's much better executed than my piece. I strongly recommend anyone...
Glitch - Building Glitch
You go to the building with the lights (not the empire state building) and on one of the sides you go in and go down slow with the helicopter and your under the city.
To get 100% you have to complete the following:
* Complete all Main Missions.
* Complete all 10 Drug Deliveries.
* Complete all 10 Races.
* Complete all 10 Assassination missions.
* Complete all 30 car thefts.
* Collect all 10 cars for the Exotic Exports mission.
* Unlock all five friend's special abilities and complete the activities with Little Jacob, Brucie and Packie.
* Beat the computer or an online friend in all activities.
* Find all Random Characters and complete their missions (except for Jeff, Cherise, Clarence & Ivan).
* Complete all 30 Most Wanted Missions.
* Complete all 20 Vigilante Missions.
* Kill all 200 Pigeons.
* Complete all 50 Unique Jumps.
If you go to an Internet café and enters the URL www.whattheydonotwantyout oknow.com you will get to a page with maps of all weapon pickups, health, armor, vehicle locations, unique jumps and pigeon locations.
If you call 911 on your phone you can select if you need an ambulance, police car or a fire truck. Make your selection and wait for them to arrive so you can steal the vehicle. If you get into the ambulance you will get a small health boost and if you get into the police car you will get 5 shotgun shells.
Get Claude's outfit:
If you choose the kill Playboy X you will take over his safehouse. If you change clothes in that safehouse you can choose to wear the outfit Claude (the main character in GTA III) was wearing. Black jacket, green pants and black/white shoes.
Get to Happiness Island. Run up to the base of the statue to find a shirt on the ground. Walk over it to put it on. It has a picture of the statue and the text Happiness is... on the front and the text ...land on the back.
The heart of the Statue:
Get a helicopter and fly to Happiness Island. Jump out of the helicopter at the top of the statue's base so you'll land by it's feet. You can not take the stairs this high. Look at the sign next to the door. It says No Hidden Content Here. Enter the door and climb the ladder inside the statue. You will find a big, red, beating heart held in place by chains.
Head inside the old, abandoned Casino where the last mission takes place, at the north end of Alderney. Look at one of the trash piles on the ground to find a purple *** sticking out.
Across the road from Bank of Liberty you can find a house covered in graffitti. Some of the artwork is from old GTA titles.
Across the street from the museum in Algonquin you can find a portrait painter. The portraits are of old GTA characters.
Old GTA character's names graffitti:
Go inside one of the pink houses near Manny's community center. Go to the back of the inside and look at the wall. You will find graffitti with names from a lot of old GTA characters, like Claude, Tommy, Toni, etc.
OG Loc CD:
In your Bohan safehouse you can find a CD by OG Loc from San Andreas on the floor.
Golf Course Land Marks:
At the mini-golf course at Firefly Island you can find a small version of the giant chicken from San Andreas, the lighthouse from the GTA III version of Liberty City, the Watts Towers from Los Santos and the Ocean View Hotel from GTA: Vice City.
Easy One Man Army achievement:
To get the One Man Army achivement steal or spawn a helicopter and fly over an island that you don't have access to yet. It will raise your wanted level to 5 stars. Fly as high as you can and you'll be flying higher than the police helicopters, then just fly for 5 minutes.
Car repair glitch:
When your car breaks down and it wont start, get your phone up and type 911. As soon as your call gets through your car will start up again. (This also works for any other number including pre-set ones i.e. Roman's). It works for every vehicle.
Easy Gobble Gobble Achievement:
Go to the bowling alley that you took Michelle on a date to. Choose the left most lane. Move Niko to the left 2 full steps. Throw the ball slowly, you want the speed somewhere around 20 but it doesn't need to be exact. Do this three times.
Easy Walk Free Achievement:
Go to the northern most road in Bohan, the small island where you get a safehouse after your first one gets burned down. There is a point where the elevated train tracks come down and go into a tunnel. Stand beside that place and shoot people and cops until you get 4 stars. Then jump or drive over the edge and land on the train tracks below and head into the tunnel. Just keep going until you are out of the search radius and you lose you wanted level. But to do this you will need to have unlocked the island of Algonquin (the middle one) or else you'll get 6 stars for crossing under the river.
Easy One Man Army Achievement:
At the start of the game drive north to Bohan, the island where you get a safehouse after your first one is burned down. At the very northern most road there is a point where the subway train tracks go from an elevated line to underground. Drive a car from the road onto the tracks and head into the tunnel. Eventually you'll cross the river and end up on the locked island of Algonquin and receive 6 stars. Stay in the tunnel for 5 minutes and you'll get the achievement.
Enter Codes by pressing up on the D-Pad to bring up your cell phone screen than pressing D-Pad again to bring up the number pad. Than enter one of the following phone numbers for the desired effect.
Warning:Using Cheat Codes will disable certain achievements!
Boom? (Call Packie for him to make you a car bomb)
Gain 75% friendship with Packie
Chopper Ride (He will pick you up in his helicopter)
Gain 70% Friendship with Brucie
Discount Guns (Buy weapons at a cheaper price from Lil Jacob)
Gain 60% friendship with Little Jacob
Extra Help (A car of gang members will be sent to help you out)
Gain 60% friendship with Dwayne
Free Ride (Call for a taxi)
Gain 60% friendship with Roman
Health Boost (Call Carmen and select "Health Boost")
Get 80% Relationship Status with Carmen
Remove Up to 3 Wanted Stars (Call Kiki and select "Remove Wanted")
Get 80% Relationship Status with Kiki
Use the following trick to make any vehicle immune to rockets, grenades, and other weapons. Take out a girlfriend on a date. Get in your car and shoot through your window to do a drive-by to scare her. A short intermission sequence will show your date leaving. Your vehicle is now immune to damage.
Get a Statue of Happiness Sweater
Go to the statue of Happiness and walk up to the second level. Walk through the door (it doesn't swing open, just go through it) and you will walk out with a sweater that has the statue of Happiness on it.
Don't Pay Tolls
Use any emergency vehicle, such as a police car or ambulance, and turn on the sirens. Drive through the booth and the attendant will open the gate and you'll save $5.
Item Locations on the Map
Go to an in-game computers and enter www.whattheydonotwantyoutoknow.com to unlock map locations for weapons, health, armor, vehicles, pigeons, ramps/stunts, and entertainment.
The Heart of Liberty City
You have to have access to Happiness Island or use a cheat code to spawn a helicopter. Alternately you can find the Helicopter Tours (directly east of Happiness Island) and steal a helicopter. Fly to Happiness Island and once you get over the Statue of Liberty, jump out of the helicopter at the statue's feet. You should land on the topmost part of the statue, which is basically a square platform with a door in the center of each side. Run around the platform until you see a door with a plaque on either side of it that reads, "No Hidden Content Here." The door doesn't open. You have to walk THROUGH the door. Inside, you'll find an empty room with a tall ladder. Climb it, and when you reach the top, look up; there is a surprise waiting for you.
Go to an ATM and cause a traffic jam in the area. Wait for someone to take money out of the ATM, then kill them. Make sure you have blocked any nearby roads so an ambulance can't get to the victim. Take the money they dropped then run a short distance away and go back. The money should respawn on the ground. You can repeat this as many times as you want. You can also kill more people and take their money from the ATM to increase the amount that respawns.
Get Your Engine Running
If your vehicle breaks down and the engine will not start, simply call 911, and your engine should be up and running.
Honk your Horn
Get any car and go to a traffic jam. Honk the horn to the beat of "Shave and a haircut" and stop, one of the other cars should respond with "two bits". Listen carefully, it might be done by a pedestrian instead.
Mr. tasty and the GTA Theme
When inside a Mr. Tasty truck, one of the the songs the truck plays is the GTA Theme. While playing the song, call ZiT, and a text message will confirm telling you the name of the song. As soon as the message is received, a Cheat confirmation will appear. The cheat will be in the Cheat section of your phone now as well.
It gives you full healith and Body Armor
The Lost and Damned DLC Achievements
How to Unlock
Easy Rider (100)
Finish the story.
Full Chat (70)
Build Terry and Clay's toughness to 100%.
Get Good Wood (50)
In the bike races, whack off 69 bikers with a bat.
One Percenter (5)
Help Billy get his bike back.
The Lost Boy (25)
Become leader of The Lost.
Off the Boat (5 points): Complete the first mission.
One Hundred and Eighty (10 points): In a darts game score 180 with three darts.
Pool Shark (10 points): Defeat a friend at pool.
King of QUB3D (15 points): Beat the high score in QUB3D.
Finish Him (15 points): Complete ten melee counters in four minutes.
Genetically Superior (25 points): Come first in twenty single player street races.
Wheelie Rider (30 points): Do a wheelie lasting at least 500 feet on a motorbike.
Gobble Gobble (10 points): Score three strikes in a row (a turkey), in ten-pin bowling.
Driving Mr. Bellic (10 points): Unlock the special ability of taxi.
Rolled Over (30 points): Do five car rolls in a row from one crash.
Walk Free (50 points): Lose a four star wanted rating by outrunning the cops.
Courier Service (10 points): Complete all ten package delivery jobs.
Retail Therapy (10 points): Unlock the special ability of buying guns from a friend.
Chain Reaction (20 points): You must blow up ten vehicles in ten seconds.
One Man Army (40 points): Survive five minutes on a six star wanted level.
Lowest Point (5 points): Complete mission "Roman's Sorrow".
Over Fulfilled (10 points): Complete all ten Exotic Export orders.
Manhunt (15 points): Complete the most wanted side missions from the police
Cleaned the Mean Streets (20 points): Capture twenty criminals through the police
Fed The Fish (5 points): Complete the mission "Uncle Vlad".
It'll Cost Ya (5 points): Complete a taxi ride without skipping from one island to another.
Sightseer (5 points): Fly on all helicopter tours of Liberty City.
Warm Coffee (5 points): Successfully date a girl to be invited into her house.
That's How We Roll! (10 points): Unlock the special ability of a helicopter.
Half Million (55 points): Reach a balance of $500,000.