Unlockable: Equipment
The following weapons and equipment can be unlocked by attaining the (multiplayer) levels below:
Assault Rifles
FAMAS - Lvl. 1
M4A1 Carbine - Lvl. 4
SCAR-H - Lvl. 8
TAR-21 - Lvl. 20
FAL - Lvl. 28
M16A4 - Lvl. 40
ACR - Lvl. 48
F2000 - Lvl. 60
AK-47 - Lvl. 70
M14 EBR - Campaign Only
G3 - Campaign Only
Submachine Guns
UMP .45 - Lvl. 1
MP5k - Lvl. 4
Vector - Lvl. 12
P90 - Lvl. 24
Mini Uzi - Lvl. 44
Light Machine Guns
L86 LSW - Lvl. 1
RPD - Lvl. 4
MG4 - Lvl. 16
AUG HBAR - Lvl. 32
M240 - Lvl. 52
Sniper Rifles
CheyTac Intervention - Lvl. 1
Barrett .50 Cal (AKA M107) - Lvl. 4
WA2000 - Lvl. 36
M21 EBR - Lvl. 56
Dragunov - Campaign Only
Secondary Weapons
PP-2000 - Machine Pistols Lvl. 1
Glock 18 - Lvl. 22
M93 Raffica - Lvl. 38
TMP - Lvl. 58
Shotguns
SPAS-12 - Lvl. 1
AA-12 - Lvl. 12
Striker - Lvl. 34
Ranger - Lvl. 42
M1014 - Lvl. 54
Winchester 1887 - Lvl. 67
W1200 - Campaign Only
Handguns
USP .45 - Handguns Lvl. 1
.44 Magnum aka Colt Anaconda - Lvl. 26
M9 - Lvl. 46
Desert Eagle - Lvl. 62
M1911 - Campaign Only
Launchers
AT4-HS - Lvl. 1
Thumper x2 aka M79 grenade launcher - Lvl. 14
Stinger - Lvl. 30
Javelin - Lvl. 50
RPG-7 x2 - Lvl. 65
Other
Frag Grenade - Lvl. 1
Semtex - Lvl. 1
Throwing Knife - Lvl. 7
Tactical Insertion - Lvl. 11
Blast Shield - Lvl. 19
Claymores - Lvl. 31
C4 - Lvl. 43
Knife
Ice Picks
Smoke grenade
Stun grenade
Attachments
Red Dot Sight
EOTech Holographic Weapon Sight
MARS Sight
ACOG Sight (and various telescopic sights that are specific to certain guns)
Thermal Scope
Suppressor
Grenade Launcher
Heartbeat Sensor
Shotgun
Extended Magazine
Full Metal Jacket ammunition (replacement for Deep Impact)
Sniper Scope (will not take up an attachment slot, just like in Call of Duty 4)
Akimbo
Rapid Fire (replacement for Double Tap)
Foregrip
Tactical Knife
Unlockable: Extra Custom Class Slot
Reach level 70 in multiplayer and enter Prestige Mode to unlock an additional custom class slot for a total of six.
Unlockable: Professional Perks
Upgrade perks by performing the actions below:
Bling Pro / 2 Primary Weapon Attachments + 2 Secondary Weapon Attachments - Get 200 kills with a Weapon with two attachments
Cold-Blooded Pro / Hidden from UAV, air support, sentries, and thermal imaging + No Red Crosshair or Name when you are Targeted - Destroy 40 enemy Killstreak Rewards with Cold-Blooded Perk
Commando Pro / Increased melee distance + No falling damage - Get 20 Melee Kills using Commando Perk
Danger Close Pro / Increased explosive weapon damage + Extra air support damage - Get 100 Kills with explosives while using Danger Close Perk
Hardline Pro / Killstreak rewards require 1 less kill + Deathstreak rewards require 1 less Ddeath - Get 40 Killstreaks (2 or more in a row without dying) with Hardline Perk
Lightweight Pro / Move faster + Quick aim after sprinting - Run 30 miles with Lightweight Perk
Marathon Pro / Unlimited sprint + Climb faster - Run 26 miles with Marathon Perk
Ninja Pro / Invisible to heartbeat sensors + Your footsteps are silent - Get 50 close range kills using Ninja Perk
Scavenger Pro / Resupply from dead enemies + Extra mags - Resupply 100 times with Scavenger Perk
Scrambler Pro / Jam enemy radar near you + delay enemy claymore explosions - Get 50 close range kills using Scrambler Perk
Sitrep Pro / Detect enemy explosives and tactical insertions + Louder Enemy Footsteps - Destroy 120 detected explosives or tactical insertions with Sitrep Perk
Sleight of Hand Pro / Faster reloading + Faster aiming - Get 120 kills with Sleight of Hand Perk
Steady Aim Pro / Increased hip shot Accuracy + Longer breath hold duration - Get 80 hip shot kills using Steady Aim
Stopping Power Pro / Extra bullet damage + Extra damage to enemy vehicles - Get 300 kills with Stopping Power Perk
Unlockable: Camos
Complete the Ghillie in the Mist challenge to unlock different camos (ghillie suits) for use with your sniper classes:
Arctic camo - Get 50 one-shot kills with sniper rifles
Urban camo - Get 100 one-shot kills with sniper rifles
Desert camo - Get 200 one-shot kills with sniper rifles