1st Lieutenant
Level 28: AK-74U Submachine Gun
Level 29: Double Tab Perk Class 2
Level 30: Killer Challenges
Captain
Level 31: M1014 Shotgun
Level 32: Bandolier Perk Class 1
Level 33: Killer Challenges 2
Major
Level 34: R700 Sniper Rifle
Level 35: Eavesdrop Perk Class 3
Level 36: Killer Challenges 3
Lieutenant Colonel
Level 37: G36C Assault Rifle
Level 38: Overkill Perk Class 2
Level 39: Killer Challenges 4
Colonel
Level 40: P90 Submachine Gun
Level 41: Frag x 3 Perk Class 1
Level 42: Humiliation Challenges
Brigadier General
Level 43: Desert Eagle Pistol
Level 44: Dead Silence Perk Class 3
Level 45: Humiliation Challenges 2
Major General
Level 46: M14 Assault Rifle
Level 47: Humiliation Challenges 3
Level 48: Humiliation Challenges 4
Lieutenant General
Level 49: Barret Sniper Rifle
Level 50: Humiliation Challenges 5
Level 51: Elite Challenges
General
Level 52: MP44 Assault Rifle
Level 53: Elite Challenges 2
Level 54: Elite Challenges 3
Commander
Level 55: Commander Prestige Mode and Golden Desert Eagle
Epilogue mission
Successfully complete the game and watch the entire credits to unlock the bonus Epilogue mission.
Mile High Club mission
Complete Story mode under any difficulty setting.
Prestige mode
Reach level 55. This is a multiplayer-only mode that starts you again at level 1.