Big Boss Emblem Shortcut
Shooting a barrel that kills PMCs does NOT count as a kill (just like MGS3).

Finding Online Friends
Trying to find a friend on Metal Gear Online?

That may because they need to log into their MGO account (and onto a server) before you can find them. Plus, you "add" their MGO character name to your Friends List (for Metal Gear Online only), not any other Playstation Network game.

100K Drebin
When entering the password into Otacon's terminal, input 14983

Yes, it is incorrect, but Snake will (invisibly) gain 100K of Drebin. Run through the game a few more times with this and the no kills and no alerts bonuses, and you should gather a large sum of Drebin.

iPod Tunes
Description: Snake's iPod can download specific tunes throughout the game. Some songs have an additional "secret" effect when it is played in the game. COOL!

Beyond the Bounds -
Location: Stage 4 Shadow Moses, Tank Hangar
After power is restored, backtrack to the upper catwalk and explore all rooms. When played, this tune increases stun damage done by Snake from non-lethal weapons.

Big Boss - Earn the Big Boss emblem (see another code on this page for the criteria). This tune will increase stun damage as above and increases Snake's accuracy when played.

Bio-hazard -
Location: Stage 3 Europe, Midtown.
Hold-up a resistance soldier and perform a body search. This tune will cause soldiers held by Snake to scream in terror.

Destiny's Call - A random gift from a militia or rebel soldier if Snake gives them a healing item. Naturally, the faction should be allied or neutral, or they will not reciprocate. This tune will cause soldiers held by Snake to go enraged.

Flowing Destiny -
Location: Stage 4 Shadow Moses, Canyon
Before leaving the canyon area, examine the rocky walls for a hole hiding this item. This tune will cause soldiers held by Snake to weep like a little girl.

Fury, The -
Location: Stage 2 South America, Cove Valley Village
Inside the fire ravaged house. This tune will cause soldiers held by Snake to go enraged.

MGS 4 Love Theme / Action - A random gift from a militia or rebel soldier if Snake gives them a healing item. Naturally, the faction should be allied or neutral, or they will not reciprocate. This tune will cause soldiers held by Snake to weep like a little girl.

Opening - Old L.A. 2040 -
Location: Stage 4 Shadow Moses, Nuclear Warhead Storage B2
Input 78925 into Otacon's lab computer. This tune will increase Snake's accuracy.

Policenaughts Ending -
Location: Stage 4 Shadow Moses, Nuclear Warhead Storage B2
Input 13462 into Otacon's lab computer. This tune will cause soldiers held by Snake to fall asleep on touch.

Rock Me -
Location: Stage 2 South America, Confinement Facility
Island in the south-eastern quadrant. This tune increases Snake's amount of life recovered from items and other means.

Sailor -
Location: Stage 2 South America, Vista Mansion
Between the east wall and a cargo container. This tune increases Snake's amount of life recovered from items and other means.

Show Time - A random gift from a militia or rebel soldier if Snake gives them a healing item. Naturally, the faction should be allied or neutral, or they will not reciprocate. This tune will cause soldiers held by Snake to scream in terror.

Snake Eater - Description: Unlocked by earning all 40 game clear emblems.
This tune will increase the life recovery rate of Snake through items and other actions.

Subsistence - Play at least one game of Metal Gear Online. You must start the match with at least two players (and not simply wander around alone or on the Training Servers). This tune will increase Snake's accuracy.

Under-handed-ness
Description: Throw your grenades under-handed

How to: Lightly holding the L1 button (or your aim button, if you changed your controls), instead of holding it down completely.

SOCOM Mk,23
Although you can enter a password to get the Heckler and Koch Mk.23 SOCOM pistol (handgun from the first Metal Gear Solid), you can easily pick one up from underneath the transport truck at Shadow Moses Island's Helipad.

Emblems

Ant Emblem	Shake 50 enemies for items
Assassin's Emblem	Beat the game with 50+ knife kills, 50+ CQC holds, and 25 or less alerts
Bear Emblem	Choke 100 enemies to death
Bee Emblem	Use the Scanning Plug S or the Syringe on 50 enemies
Big Boss Emblem	Beat the game on the highest difficulty with no deaths, no alerts, no kills, no recovery items, no stealth suit, no bandanna items, in under 5 hours
Blue Bird Emblem	Give friendly soldiers 50 items
Eagle Emblem	Get 150 headshots
Fox Emblem	Finish the game on normal or higher w/ no deaths, 5 or less alerts, no kills, no recovery items, no stealth suit, no bandanna items, in under 6 hours
Fox Hound Emblem	Finish the game on hard or higher w/ no deaths, 3 or less alerts, no kills, no recovery items, no stealth suit, no bandanna items, in under 5.5 hours
Frog Emblem	Dive or roll 200 times
Gecko Emblem	Press against walls for a total of 1 hour
Giant Panda Emblem	Complete the game after 30 cumulative hours of play
Gibbon Emblem	Hold up 50 enemies
Hawk Emblem	Get liked by 25 friendly soldiers
Hog Emblem	Get 10 combat highs
Hound Emblem	Finish the game on hard or higher w/ no deaths, 3 or less alerts, no kills, no recovery items, no stealth suit, no bandanna items, in under 6.5 hours
Hyena Emblem	Pick up 400 dropped weapons
Inch Worm Emblem	Crawl on the ground for a total of 1 hour
Little Gray Emblem	Obtain all 69 weapons
Lobster Emblem	Spend a total of 2.5 hours crouching
Rabbit Emblem	Look at 100 Playboy pages

Bonus Weapon List
World War I Pistol - Earn the Hound emblem on a single-player session by doing the following:
1) Instigate no more than 3 alerts (the third alert means failure looser!)
2) Kill no enemies ,not even bosses
3) Do not continue at all
4) Do not use life recovery items at all
5) Do not use the stealth suit or bandanna special items (you may possess, but not activate them);
6) Complete the game on Naked Normal difficulty (or higher) under 6 hours and 30 minutes.

Desert Eagle, Long Barrel - Earn the Fox emblem on a single-player session by doing the following:
1) Instigate no more than 5 alerts (the fifth alert means failure looser!)
2) Kill no enemies not even bosses
3) Do not continue at all
4) Do not use life recovery items at all
5) Do not use the stealth suit or bandanna special items (you may possess, but not activate them)
6) complete the game on Naked Normal difficulty (or higher) under 6 hours.

Thor 45-70 - Earn the Fox Hound emblem on a single-player session by doing the following:
1) instigate no more than 3 alerts (the third alert means failure looser!)
2) kill no enemies not even bosses
3) Do not continue at all
4) Do not use life recovery items at all
5) Do not use the stealth suit or bandanna special items (you may possess, but not activate them)
6) complete the game on Big Boss Hard difficulty (or higher) under 5 hours and 30 minutes.

Patriot Future Assault Weapon - Earn the Big Boss emblem on a single-player session by doing the following:
1) instigate no alerts
2) kill no enemies not even bosses
3) Do not continue at all
4) Do not use life recovery items at all
5) Do not use the stealth suit or bandanna special items (you may possess, but not activate them)
6) complete the game on Big Boss Extreme difficulty under 5 hours.

Race (Ricochet) Gun - Clear the single-player game once.

Solar Gun - Collect the five statues (those of the four Battle Beauties (Beast Form) and the Frog Soldier/Haven Troopers in stage 1) using non-lethal means on their respective idols.

Frog Statue - Stage 1 Middle East, Advent Palace garage, after the Rat Patrol and Frog Trooper garage shoot-out, check behind Snake.

Octopus Statue - Stage 2 South America, Research Lab boss room, on a bed in the room during the human phase of the boss fight.

Raven Statue - Stage 3 Europe, top floor of the human phase of the boss fight.

Wolf Statue - Stage 4 Shadow Moses, behind Snake's begining spot in the human phase of the boss fight.

Mantis Statue - Stage 5 Outer Heaven, near the northern most door during the human phase of the fight (use your map).

Scanning Plug S - Log more than 10 hours of Metal Gear Online play time on the same profile as your Metal Gear 4 game. You purchase this from Drebin.

Digital Camera - In the Nomad vehicle during the mission intermission; you can unlock a special photo by picking up this item in stage 4 instead of earlier.

Stealth Item - Complete a single-player session without instigating a single alert (caution is okay, but not alert). You can do this on any difficulty.

Bandanna - Complete a single-player session without killing anyone (including bosses). You can do this on any difficulty.

Facepaint
FaceCamo - Defeat the Battle Beauty Laughing Octopus ** the overall battle, no specifics involved

Laughing Octopus - Defeat the Battle Beauty (human form) Laughing Octopus by non-lethal means.

Raging Raven - Defeat the Battle Beauty (human form) Raging Raven by non-lethal means.

Crying Wolf - Defeat the Battle Beauty (human form) Crying Wolf by non-lethal means.

Screaming Mantis - Defeat the Battle Beauty (human form) Screaming Mantis by non-lethal means.

Roy Campbell - Shock Colonel Campbell using the Metal Gear II during the intermission scene.

Otacon - Shock Dr. Emmerich using the Metal Gear II during the intermission scene.

Raiden Mask A - Shock Sunny using the Metal Gear II during the intermission scene.

Raiden Mask B - Shock Dr. Naomi Hunter using the Metal Gear II during the intermission scene.

Drebin - Purchase and keep more than 60 different weapons.

Big Boss - Earn the Big Boss emblem on a single-player session by doing the following:
1) instigate no alerts
2) kill no enemies not even bosses
3) Do not continue at all
4) Do not use life recovery items at all
5) Do not use the stealth suit or bandanna special items (you may possess, but not activate them)
6) complete the game on Big Boss Extreme difficulty under 5 hours.

New Difficulty
Earn the final level of difficulty "Big Boss Extreme" by completing the single-player mode once (and saving the cleared data). Load the cleared data to gain your benefits.

No Camo
Shake the Sixaxis controller to return Snake's Octocamo to its neutral (black & blue) colors.

Costumes / Skins
Business Suit - Clear single-player mode once.

Altair's Rags - Earn the Assassin's emblem on a single-player session by doing the following: kill or stun 50 or more enemies; CQC hold 50 or more enemies; and be discovered fewer than 25 times.

Inheritence/ Reply Tip
You can carry over your Drebin points, ammunition, weapons, items, and special items from a previous game upon completing the game. However, Snake will need to encounter Metal Gear II in the first stage to get his stuff back.
Be sure to save your cleared data upon game completion to track your items. Load the cleared data to reap your benefits.

Big Boss Tips
Location: (Act 3)
Description: Frustrated by the hardiness of Extreme difficulty? Here is a a tip

Press Triangle during the bike chase to take cover behind Eva. She cannot die during the bike chase, but Snake sure can!

Combat Vests
Clear the single-player game once to unlock new combat vests for Snake.

Stealth Tips (Online )
When playing in the online sneaking mode as Snake, you should avoid lit areas so your shadow will not be as apparent. Also a breath tip: while in stages where characters emit frosty breath, have Snake play dead while prone to make Snake's breath disappear.

Meryl's Desert Eagle (LB)
Upon completing the game, you have the option to go into the EXTRAS menu and input PASSWORDS for more items. Enter the following code for a weapon you cannot get anywhere else:
deskyhstyl

Extra Music
Location: In Act 4,
Description: Enter the following codes (once per game) to unlock more iPod music:
78925
13462

Upon completing the game, you have the option to go into the EXTRAS menu and input PASSWORDS for more items. Enter the following codes for more iPod music:
thomas
george
theodore
abraham