Reach the following ranks on Multiplayer to unlock the desired Multiplayer unlockable.

Multiplayer unlockable	How to unlock
.357 Magnum	Reach Level 49
Arisaka	Reach Level 4
Bandolier	Reach Level 40
BAR	Reach Level 4
Bomb Squad	Reach Level 16
Bouncing Betty x2	Reach level 24
Browning M1919	Reach Level 61
Camoflauge	Reach level 12
Colt M1911	Reach Level 3
Custom Class Slot 10	Reach Prestige Level 10
Custom Class Slot 6	Reach Prestige level 1
Custom Class Slot 7	Reach Prestige Level 2
Custom Class Slot 8	Reach Prestige Level 4
Custom Class Slot 9	Reach Presige Level 7
Dead Slience	Reach level 52
Deep Impact	Reach Rank 1
Double Tap	Reach Rank 36
Double-Barreled Shotgun	Reach Level 29
DP-28	Reach Level 13
Extreme Conditioning	Reach Rank 1
FG-42	Reach Level 45
Fireproof	Reach Level 48
Fireworks	Reach evel 1
Flak Jacket	Reach Level 1
Gas Mask	Reach Level 2
Gewher 47	Reach Level 6
Juggernaut	Reach Level 4
Kar98k	Reach Level 41
M1 Garand	Reach Level 17
M1A1 Carbine	Reach Level 65
M2 Flamethrower	Reach Level 65
M9A1 Bazooka x2	Reach Level 2
Martydom	Reach Level 20
MG-42	Reach Level 33
Mosin-Nagant	Reach Level 21
MP-40	Reach Level 10
Nambu	Reach Level 1
Overkill	Reach Level 56
PPSh 41	Reach Level 53
Prestige Mode	Reach Level 65
Primary Grenades x2	Reach Level 44
PTRS 41	Reach Level 57
Satchel Charge x2	Reach Level 1
Second Chance	Reach Level 9
Sleight of Hand	Reach Level 28
Special Grenades x3	Reach Level 1
Springfield	Reach Level 3
Steady Aim	Reach Level 1
STG-44	Reach Level 37
Stopping Power	Reach Level 1
SVT-40	Reach Level 1
Thompson	Reach Level 1
Tokarev TT38	Reach Level 21
Toss Back	Reach Level 6
Trench Gun	Reach Level 2
Type 100	Reach Level 25
Type 99	Reach Level 1
Walther P38	Reach Level 2