Reach the indicated rank in Multiplayer mode to unlock the corresponding bonus:

Private

Level 1: All starting equipment
Level 2: Demolitions Class Weapon Class
Level 3: Sniper Class Weapon Class

Lance Corporal

Level 4: Create a Class
Level 5: Gun Challenges
Level 6: New playlists

Corporal

Level 7: M40 Sniper Rifle
Level 8: Last Stand Perk Class 3
Level 9: Boot Camp Challenges 1

Sergeant

Level 10: M4 Carbine Assault Rifle
Level 11: UAV Jammer Perk Class 2
Level 12: Clan Tag

Staff Sergeant

Level 13: Mini Uzi Submachine Gun
Level 14: Bomb Squad Perk Class 1
Level 15: Boot Camp Challenges 2

Gunnery Sergeant

Level 16: M1911 Pistol
Level 17: Martyrdom Perk Class 2
Level 18: Boot Camp Challenges 3

Master Sergeant

Level 19: M60E4 Light Machine Gun
Level 20: Sleight of Hand Perk Class 2
Level 21: Operations Challenges

Master Gunnery Sergeant

Level 22: Dragunov Sniper Rifle
Level 23: Claymore Perk Class 1
Level 24: Operations Challenges 2

2nd Lieutenant

Level 25: G3 Assault Rifle
Level 26: Iron Lungs Perk Class 3
Level 27: Operations Challenges 3

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
Level 55: Commander Prestige Mode and Golden Desert Eagle