Primary Weapons
Assault Rifles
• M4A1: Unlocked at Level 4. Fully automatic, all purpose weapon.
• FAMAS: Unlocked at Level 1. 3-round burst.
• SCAR-H: Unlocked at Level 8. Fully automatic, all purpose weapon.
• TAR-21: Unlocked at Level 20. Fully automatic, all purpose weapon.
• FAL: Unlocked at Level 28. Semi-automatic.
• M16A4: Unlocked at Level 40. 3-round burst.
• ACR: Unlocked at Level 48. Fully automatic, all purpose weapon.
• F2000: Unlocked at Level 60. Fully automatic, all purpose weapon.
• AK-47: Unlocked at Level 70. Fully automatic, all purpose weapon.
Challenges/Attachments
• Marksman I: 10 kills with the weapon - Unlocks M203/GP-25.
• 20 kills with Grenade Launcher - Unlocks Shotgun (attachment).
• Marksman II: 25 kills with the weapon - Unlocks Red Dot Sight.
• 60 kills aiming down Red Dot Sight - Unlocks Holographic Sight.
• Marksman III: 75 kills with the weapon - Unlocks Silencer.
• 15 kills with Silencer - Unlocks Heartbeat Sensor.
• Marksman IV: 150 kills with the weapon - Unlocks ACOG Scope.
• 20 kills aiming down the ACOG - Unlocks Thermal Scope
• Marksman V: 300 kills with the weapon - Unlocks FMJ rounds.
• 40 kills with bullet penetration using FMJ - Unlocks Extended Magazines.
NOTE: The AK-47 unlocks the GP-25, not the M203.
Submachine Guns
• UMP .45: Unlocked at Level 1. Fully Automatic, close range.
• MP5k: Unlocked at Level 4. Fully Automatic, close range.
• Vector: Unlocked at Level 12. Fully Automatic, high fire rate.
• P90: Unlocked at Level 24. Fully Automatic, large magazines.
• Mini-Uzi: Unlocked at Level 44. Fully Automatic, close range.
Challenges/Attachments
• Marksman I: 10 kills with the weapon - Unlocks Rapid Fire.
• 30 kills with Rapid Fire - Unlocks Akimbo.
• Marksman II: 25 kills with the weapon - Unlocks Red Dot Sight.
• 60 kills aiming down Red Dot Sight - Unlocks Holographic Sight.
• Marksman III: 75 kills with the weapon - Unlocks Silencer.
• Marksman IV: 150 kills with the weapon - Unlocks ACOG Scope.
• 20 kills aiming down the ACOG - Unlocks Thermal Scope.
• Marksman V: 300 kills with the weapon - Unlocks FMJ rounds.
• 40 kills with bullet penetration using FMJ - Unlocks Extended Magazines.
Light Machine Guns
• L86 LSW: Unlocked at Level 3. Fully Automatic, large magazines.
• RPD: Unlocked at Level 4. Fully Automatic, large magazines.
• MG4: Unlocked at Level 16. Fully Automatic, large magazines.
• AUG HBAR: Unlocked at Level 32. Fully Automatic, high accuracy and damage.
• M240: Unlocked at Level 52. Fully Automatic, large magazines.
Challenges/Attachments
• Marksman I: 10 kills with the weapon - Unlocks Grip.
• Marksman II: 25 kills with the weapon - Unlocks Red Dot Sight.
• 60 kills aiming down Red Dot Sight - Holographic Sight
• Marksman III: 75 kills with the weapon - Unlocks Silencer.
• 15 kills with silencer - Unlocks Heartbeat Sensor.
• Marksman IV: 150 kills with the weapon - Unlocks ACOG Scope.
• 20 kills aiming down the ACOG - Unlocks Thermal Scope.
• Marksman V: 300 kills with the weapon - Unlocks FMJ rounds.
• 40 kills with bullet penetration using FMJ - Unlocks Extended Magazines.
NOTE: The MG4 incorrectly states that FMJ rounds are explosive rounds.
Sniper Rifles
• Intervention: Unlocked at Level 4. Bolt-Action.
• Barrett .50cal: Unlocked at Level 4. Semi-Automatic.
• WA2000: Unlocked at Level 36. Semi-Automatic.
• M21 EBR: Unlocked at Level 56. Semi-Automatic.
Challenges/Attachments
• Marksman I: 10 kills with the weapon - Unlocks Silencer.
• 15 kills with the Silencer - Unlocks Heartbeat Sensor.
• Marksman II: 25 kills with the weapon - Unlocks ACOG Scope.
• 20 kills aiming down the ACOG - Unlocks Thermal Scope.
• Marksman III: 75 kills with the weapon - Unlocks FMJ rounds.
• 40 kills with bullet penetration using FMJ - Unlocks Extended Mags.
Riot Shield
Riot Shield: Unlocked at Level 4. Provides protection from bullet damage.
Challenges
• Sponge I, II, III: Absorb 1000/10,000/100,000 damage with your shield.
• Bulletproof: Deflect 1000 Bullets from your shield.
• Backsmasher: Smash an enemy in the back with the Riot Shield.
• Unbreakable: Get a 3 killstreak with the Riot Shield.
Secondary Weapons
Machine Pistols
• PP2000: Unlocked at Level 3. Fully Automatic, close range.
• G18: Unlocked at Level 22. Fully Automatic, close range.
• M93 Raffica: Unlocked at Level 38. 3-round burst, close range.
• TMP: Unlocked at Level 58. Fully Automatic, close range.
Challenges/Attachments
• Marksman I: 10 kills with the weapon - Unlocks Red Dot Sight.
• Marksman II: 25 kills with the weapon - Unlocks Silencer.
• Marksman III: 50 kills with the weapon - Unlocks FMJ.
• Marksman IV: 75 kills with the weapon - Unlocks Akimbo.
• Marksman V: 100 kills with the weapon - Unlocks Holographic Sight.
• Marksman VI: 150 kills with the weapon - Unlocks Extended Magazines.
Handguns
• USP .45: Unlocked at Level 4.
• .44 Magnum: Unlocked at Level 26.
• M9: Unlocked at Level 46.
• Desert Eagle: Unlocked at Level 62.
Challenges/Attachments
• Marksman I: 10 kills with the weapon - Unlocks FMJ.
• Marksman II: 25 kills with the weapon - Unlocks Silencer.
• Marksman III: 50 kills with the weapon - Unlocks Akimbo.
• Marksman IV: 75 kills with the weapon - Unlocks Tactical Knife.
• Marksman V: 100 kills with the weapon - Unlocks Extended Magazines.
NOTE: Both the Desert Eagle and the .44 Magnum cannot accept a suppressor or extended magazines.
Shotguns
• SPAS-12: Unlocked at Level 1. Pump-Action.
• AA-12: Unlocked at Level 18. Fully Automatic, low ammo.
• Striker: Unlocked at Level 34. Semi-Automatic.
• Ranger: Unlocked at Level 42. Double barreled.
• M1014: Unlocked at Level 54. Semi-Automatic.
• Model 1887: Unlocked at Level 67. Lever-Action.
Challenges/Attachments
• Marksman I: 10 kills with the weapon - Unlocks Red Dot Sight.
• Marksman II: 25 kills with the weapon - Unlocks Silencer.
• Marksman III: 75 kills with the weapon - Unlocks FMJ.
• Marksman IV: 150 kills with the weapon - Unlocks Grip.
• Marksman V: 250 kills with the weapon - Unlocks Holographic Sight.
• Marksman VI: 400 kills with the weapon - Unlocks Extended Magazines.
NOTE: Both the Ranger and the Model 1887 can only accept the Akimbo and FMJ attachments. These attachments are unlocked at 10 and 50 kills respectively.
Launchers
• AT4: Unlocked at Level 4. Vehicle Lock-on or free fire.
• Thumper: Unlocked at Level 14. Unguided grenade launcher.
• Stinger: Unlocked at Level 30. Vehicle Lock-on only.
• Javelin: Unlocked at Level 50. Vehicle or location Lock-on only.
• RPG-7: Unlocked at Level 65. Unguided RPG launcher.
NOTE: The Javelin and the AT4 are the only Launchers which only have one rocket. The other launchers have two.
Equipment and Support
Equipment
• M67 Frag Grenade: Unlocked at Level 4. Cookable grenade.
• Semtex: Unlocked at Level 4. Timed explosive. Sticks to people and surfaces that it hits.
• Throwing Knife: Unlocked at Level 7. Reusable throwing blade. Throw it and pick it back up.
• Tactical Insertion: Unlocked at Level 11. A flare that marks your next respawn.
• Blast Shield: Unlocked at Level 18. Provides resistance to explosives and headshots, and grants immunity to Stun Grenades.
• Claymore: Unlocked at Level 31. Trip detonated mine.
• C4: Unlocked at Level 43. Remote detonated explosive.
Support
• Knife: Default. Standard issue fighting knife, kills in one blow and is lethal in extreme close quarters situations.
• Minigun: Found on various maps in defensive positions.
Source: www.wikia.com