Medals unlock bonus weapons and items. You are also able wear medals by equipping them in the modify agent option on the personnel screen.

Medal of Distinction: Beat single player mission deadline on all missions
Item: US M60 E3

Agency Medal of Valor: Earn all Agency ratings, special agency ratings, all commendations, all other medals, highest rank.
Item: M-249 SAW

Stone's Medal of Courage: Rescue Stone Ukraine, Provide cover fire for Stone.
Item: SPA-15 Shotgun

Carthage Exemplary Service Tribute: Carthage 1 and 2: Protect CHA officers, Carthage 2: Eliminate all 4 ALA death squad assassins, Carthage 3: Rescue injured SWAT officers
Item: Spectre

Homeland Security Citation: Earn Carthage Exemplary Service Tribute and the President's official Liberty Award. Zurich: Obtain Birchim files.
Item: FAL SG-1

Ellison Warner Award: Belarus 2: Destroy SCUD missile, Yemen 2: Destroy SCUD firing mechanism, Myanmar: Recover flight recorder
Item: Tec 45

Karkadann, Alima's Unicorn Charm: Yemen 1: Complete all objectives, Yemen 2: Complete all objectives, Ukraine: Bring Alima Haddad to safety.
Item: Desert Eliminator .357

Republic of Korea Sevice Award: Kyrgystan: Locate Yuschenko's papers, Yemen 1: Obtain Thae-bok Jon's credentials, Tokyo: Upload computer data, Myanmar: Find Yong-jun Kim's Briefcase.
Item: China type 56

South African Freedom Medal: All missions: No collateral damage, Earn Stone's Medal of Courage, Earn Carthage Exemplary Service Tribute, Belarus 1: Escort all workers to safety, Lorelei: Rescue Level 5 salvage personnel
Item: Sweeper 12 gauge

President's Official Liberty Award: Carthage 3: Complete DPE order on Masson, Italy: Assassinate Dimitriby the bell tower at 3:00 PM, Belarus 1: Eliminate Zhidkov, Kyrgyzstan: Poison Saydahmat's water chalice, Myanmar: Eliminate Than Muang.
Item: DSC-1

Great Lakes Service Medal: Carthage 1,2,3: Complete all objectives, Yemen 1: Photograph Fadhil's files, Zurich: Obtain ALA financial records.
Item: MDS-k PDW

Kinishi Kuncho: Order of the Golden Dragon: Earn Republic of Korea Sevice Award, Kyrgyszstan, Tokyo and Myanmar: Complete all objectives.
Item: SPA-12 shotgun

The Golden Cross of Russia: Belarus 1 and 2: Complete all objectives, Kyrgyzstan: complete all objectives, Yemen 1 Photograph Fadhil's files, Minsk: Complete all objectives, Montenegro: Find evidence linking Niculescu to Syphon Filter, Ukraine: Complete all objectives.
Item: TH3 Blaster

Mossad Friend to Peace Medal: Earn Karkadann, Alima's Unicorn Charm, Kyrgystan: Eliminate Zayed Al Dhahiri
Item: Galil SG-1

United Nations Peace Award: Cure the Omega Strain, Carthage 1: Scan tissue sample, Carthage 2: Obtain Mujari's recorder, Belarus 1: Take tissue sample from cow carcass, take mill documents from safe, Belarus 2: Obrain sewage sample, Yemen 2: Obtain Yushchenkos viral container, Minsk: Acquire Omega Strain serum, Lorelei: Collect original virus sample, Tokyo: Obtain sample, Ukrain:Find Omega Strain DNA code
Item: C11