# Museum bonus levelSuccessfully complete the game to unlock the Museum bonus level. Go to the single player missions, select the new "Museum" mission at the bottom, and choose a difficulty. When the level begins, it is recommended you first study the layout. Get two weapons, and max out your ammunition through the crates supplied. Go to the desks by the entrance to the rooms. On the desks there is a red bell that is labeled "Don't Press". Once you press this button, enemies will begin coming to life in one room area at a time. About thirty people (all characters from the game) will try to kill you.
You will hear a sound once that wave is completed. There are two waves of kills needed to complete it. Note: There are three rooms, one of which nothing happens in. Do not bother shooting anyone prior to using the bell, as it will not count.
# Extra Custom Class slots
Reach Level 70 in Multiplayer mode to unlock Prestige mode. Reach the indicated Prestige level to unlock the corresponding Custom Class slot.
Sixth Custom Class slot: First Prestige
Seventh Custom Class slot: Third Prestige
Eighth Custom Class slot: Fifth Prestige
Ninth Custom Class slot: Seventh Prestige
Tenth Custom Class slot: Tenth Prestige
# Professional perks
Successfully complete the indicated task to unlock the corresponding Professional perk:
Bling Pro: Get 200 kills while using a weapon with two attachments. Its effect is two primary weapon attachments and two secondary weapon attachments.
Cold-Blooded Pro: Destroy 40 enemy Killstreak rewards while using the Cold-Blooded perk. Its effect is undetectable by UAV, air support, sentries, and thermal imaging; and no red crosshair or name when you are targeted.
Commando Pro: Get 20 melee kills while using the Commando perk. Its effect is increased melee distance and no falling damage.
Danger Close Pro: Get 100 kills with explosives while using the Danger Close perk. Its effect is increased explosive weapon damage and extra air support damage.
Hardline Pro: Get 40 Killstreaks while using the Hardline perk. Its effect is that Killstreak rewards require one less kill and Deathstreak rewards require one less death.
Last Stand Pro: Get 20 kills while using the Last Stand perk. Its effect is that you can use your equipment (i.e. frag grenades and throwing knives) while in Last Stand mode.
Lightweight Pro: Run 30 Miles while using the Lightweight perk. Its effect is move faster and quick aim after sprinting.
Marathon Pro: Run 26 Miles while using the Marathon perk. Its effect is unlimited sprint and climb obstacles faster.
Ninja Pro: Get 50 close range kills while using the Ninja perk. Its effect is invisible to heartbeat sensors and silent footsteps.
Scavenger Pro: Resupply 100 times while using the Scavenger perk. Its effect is resupply from dead enemies and extra magazines.
Scrambler Pro: Get 50 close range kills while using the Scrambler perk. Its effect is jam enemy radar near you and delay enemy claymore explosions.
SitRep Pro: Destroy 120 detected explosives or tactical insertions while using the Sitrep perk. Its effect is detect enemy explosives and tactical insertions and louder enemy footsteps.
Sleight Of Hand Pro: Get 120 kills while using the Sleight Of Hand perk. Its effect is faster reloading and aiming.
Steady Aim Pro: Get 80 hip fire kills while using the Steady Aim perk. Its effect is increased hip fire accuracy and longer hold breath duration.
Stopping Power Pro: Get 300 Kills while using the Stopping Power perk. Its effect is extra bullet damage and extra damage to enemy vehicles.
# Multiplayer weapons and equipment
Reach the indicated level in Multiplayer mode to unlock the corresponding item:
Assault rifles
FAMAS: Level 1
M4A1 carbine: Level 4
SCAR-H: Level 8
TAR-21: Level 20
FAL: Level 28
M16A4: Level 40
ACR: Level 48
F2000: Level 60
AK-47: Level 70
Handguns
USP .45: Level 1
.44 Magnum (Colt Anaconda): Level 26
M9: Level 46
Desert Eagle: Level 62
Launchers
AT4-HS: Level 1
Thumper x2 (M79 grenade launcher): Level 14
Stinger: Level 30
Javelin: Level 50
RPG-7 x2: Level 65
Light machine guns
L86 LSW: Level 1
RPD: Level 4
MG4: Level 16
AUG HBAR: Level 32
M240: Level 52
Shotguns
SPAS-12: Level 1
AA-12: Level 12
Striker: Level 34
Ranger: Level 42
M1014: Level 54
Winchester 1887: Level 67
Sniper rifles
CheyTac Intervention: Level 1
Barrett .50 caliber (M107): Level 4
WA2000: Level 36
M21 EBR: Level 56
Submachine guns
UMP .45: Level 1
MP5k: Level 4
Vector: Level 12
P90: Level 24
Mini Uzi: Level 44
Secondary weapons
PP-2000 machine pistols: Level 1
Glock 18: Level 22
M93 Raffica: Level 38
TMP: Level 58
Other
Frag grenade: Level 1
Semtex: Level 1
Throwing knife: Level 7
Tactical insertion: Level 11
Blast shield: Level 19
Claymores: Level 31
C4: Level 43
# Kill streak bonuses
Get the indicated number of consecutive kills in Multiplayer mode to get the corresponding bonus:
UAV: 3 (reveals enemies on mini-map)
Care Package: 4 (ammo or killstreak air drop that can be collected by anyone)
Counter UAV: 4 (disables enemy radar)
Predator: 5 (guided missile)
Sentry Gun: 5 (airdropped weapon)
Precision Airstrike: 6 (select a location to bomb)
Attack Helicopter: 7 (helicopter backup)
Harrier Strike: 7 (select a location to bomb and defend with a Harrier)
Emergency Airdrop: 8 (four ammo or killstreak air drops that can be collected by anyone)
Pave Low: 9 (armored helicopter backup)
Stealth Bomber: 9 (undetectable airstrike)
AC-130: 11 (operate a plane gun)
Chopper Gunner: 11 (operate a helicopter gun)
EMP: 15 (disables enemy electronics)
Tactical Nuke: 25 (kills everyone)
