Admiral Difficulty Complete single player on Captain.
Captain Difficulty Complete single player on Commander.

Medium Scope Complete game on Captain

Multiplayer Characters

North Africa - Al-Kamli Sarwat (Terrorist) Complete North Africa on any difficulty.
North Africa - KILLJOY (Seal) Training Missions Completed.
North Africa - Seal Jungle Ghillie Suit Complete N.A. on either Commander, Captain, or Admiral.
North Africa - Terrorist Jungle Ghillie Suit Complete N.A. on either Commander, Captain, or Admiral.
Poland - COLDKILL (Seal) Complete Poland on any difficulty.
Poland - Dr. Basia Mironova (Terrorist) Complete Poland on any difficulty.
Poland - Seal Winter Ghillie Suit Complete Poland on either Commander, Captain, or Admiral.
Poland - Terrorist Winter Ghillie Suit Complete Poland on either Commander, Captain, or Admiral.
South Asia - CHOPPER (Seal) Complete South Asia on any difficulty.
South Asia - Hari Raman (Terrorist) Complete S.A. on Captain or Admiral.
South Asia - Seal Desert Ghillie Suit Complete S.A. on either Commander, Captain, or Admiral.
South Asia - Terrorist Desert Ghillie Suit Complete S.A. on either Commander, Captain, or Admiral.

Scarecrow character skin  -  If you achieve 24 hours played online in Socom III, the character skin "Scarecrow" is then unlocked and can be used.

Scarecrow skin for online log at least 24 hours of online play

Unlock Weapons  -  Complete the game on the Admiral difficulty to unlock the following weapons.

IW-80 A2 Complete game on Admiral difficulty
STG-77 Complete game on Admiral difficulty

Weapons for Single Player or Training.

ADMIRAL Difficulty Complete game on CAPTAIN
CAPTAIN Difficulty Complete game on COMMANDER
GROM Weapons Complete game on CAPTAIN
SBS Weapons Complete game on COMMANDER
SEAL Weapons Complete game on ENSIGN
Terrorist Weapons Complete game on LIEUTENANT

Successfully complete SOCOM 3: Fireteam Bravo on the PSP on any difficulty setting and link to SOCOM 3: U.S. Navy SEALs to unlock the COLDKILL (Poland SEAL) and Dr. Basia Mironova (Poland terrorist) characters.

Accumulate at least 24 hours of online game play time to unlock the Scarecrow character skin.

Connection bonuses - Link to a PSP with SOCOM 3 Fireteam Bravo and complete the indicated task to unlock the corresponding bonus:

Al-Kamil Sarwat (North Africa Terrorist): Successfully complete North Africa.
Chopper (South Asia SEAL): Successfully complete South Asia.
Dr. Basia Mironova (Poland Terrorist): Successfully complete Poland.
Front Grip: Successfully complete South Asia.
IW-80 A2: Successfully complete the Poland.
Medium Scope: Successfully complete the South Asia.
STG-77: Successfully complete Poland.

Avoiding snipers in Ripostes Primer - At the beginning of the mission when you rescue the ambassador, sweep the area. Once it is clear, walk up the path. When you reach the stairs, go up to the top, then turn right and walk. You will see a patch of grass and a tree. Keep going straight and you will reach a dead end. Look to the left and you will see a secret passage. Go through, and when you get to the other side there will be a guard. Kill him and move stealthily. The two snipers on the roof will not notice you there. Take them out, then continue your mission.

Sick raider in Heart Of The Fist - When you find the third crate of the ship's cargo, there is an outhouse next to the tent. If you stand in front of the door you can hear a raider complaining about the soup he ate.