You carry over your Drebin points, weapons, ammunition, items, and special items from a previous game upon game clear. 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.

Earn the final level of difficulty "Big Boss Extreme" by completing the single-player mode once (and saving the cleared data).

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

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: instigate no alerts; kill no enemies (not even bosses); do not continue (at all); do not use life recovery items (at all); do not use the stealth suit or bandanna special items (you may possess, but not activate them); and complete the game on Big Boss Extreme difficulty under 5 hours.

Snake's iPod can download specific tunes throughout the course of the game. Some songs have an additional "secret" effect when it is played in the game.

Beyond the Bounds - 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 - 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 - 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 - 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 - Stage 4 Shadow Moses, Nuclear Warhead Storage B2. Input 78925 into Otacon's lab computer. This tune will increase Snake's accuracy.

Policenaughts Ending - 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 - 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 - 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 - 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.

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.

World War I Pistol - Earn the Hound emblem on a single-player session by doing the following: instigate no more than 3 alerts (the third alert means failure); kill no enemies (not even bosses); do not continue (at all); do not use life recovery items (at all); do not use the stealth suit or bandanna special items (you may possess, but not activate them); and 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: instigate no more than 5 alerts (the fifth alert means failure); kill no enemies (not even bosses); do not continue (at all); do not use life recovery items (at all); do not use the stealth suit or bandanna special items (you may possess, but not activate them); and 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: instigate no more than 3 alerts (the third alert means failure); kill no enemies (not even bosses); do not continue (at all); do not use life recovery items (at all); do not use the stealth suit or bandanna special items (you may possess, but not activate them); and 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: instigate no alerts; kill no enemies (not even bosses); do not continue (at all); do not use life recovery items (at all); do not use the stealth suit or bandanna special items (you may possess, but not activate them); and 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 starting 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.

• 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

In Act 4, enter the following codes (once per game) to unlock more iPod ™ music:

78925

13462

Upon completing the game once, you will 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

Upon completing the game once, you will 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

Shake the Sixaxis controller to return Snake's Octocamo to its neutral (black and blue) pigmentation.

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

When entering the password into Otacon's terminal, input 14983. Although incorrect, Snake will (invisibly) gain 100K of Drebin points. Run through the game a few more times with this and the no kills and no alerts bonuses, and you should amass quite a sum of Drebin points.

Trying to find a friend on Metal Gear Online but can't? That's because a player needs to log into their MGO account (and onto a server) before you to find them. Additionally, you "add" their MGO character name to your Friends List (for Metal Gear Online only), not any other Playstation Network game.

Throw your grenades under-handed by lightly holding the L1 button (or your aim button, if you changed your controls), instead of holding it down completely.

For players who are frustrated by the hardiness of Extreme difficulty, here're a few tips for Act 3:

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

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.

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