In Mission mode reach the following Career ranking to unlock the corresponding weapons.

Unlock Sawed-Off Pistol:
Reach Survival Specialist ranking - Rating 1

Unlock TK-9 Silenced:
Reach Stealth Combat Specialist ranking - Rating 1

Unlock Flashbang Grenade:
Reach Combat Knife Specialist ranking - Rating 1

Unlock USAS - 12:
Reach Tactical Combat Specialist ranking - Rating 1

Unlock SSP 90:
Reach Combat Sharp Shooter ranking - Rating 1

Unlock C11:
Reach Combat Knife Specialist 2 ranking

Unlock Over Under:
Reach Combat Sharp Shooter ranking - Rating 2

Unlock Jerico-41:
Reach Tactical Combat Specialist ranking - Rating 2

Unlock MDS A4 Silenced:
Reach Stealth Combat Specialist ranking - Rating 2

Unlock Chinese Type 56:
Reach Combat Knife Specialist ranking - Rating 3

Unlock Silenced .44:
Reach Stealth Combat Specialist ranking - Rating 3

Unlock M4 Silenced:
Reach Survival Specialist ranking - Rating 3

Unlock M67 Grenade:
Reach Tactical Specialist ranking - Rating 3

Unlock EPDD:
Reach Stealth Combat Specialist ranking - Rating 4

Unlock M82 BFG:
Reach Combat Sharp Shooter ranking - Rating 4

Unlock Calico HE:
Reach Survival Specialist ranking - Rating 4

Unlock Jackhammer HE:
Reach Tactical Combat Specialist ranking - Rating 4

Unlock SP - 57:
Complete Training 1 in less than 1 minute and 30 seconds

Unlock FAMAS:
Complete Training 2 in less than 3 minutes

Unlock UNP .45:
Complete Training 3 without wasting a shoot

In Mission mode reach the indicated career ranking to unlock the corresponding abilities and upgrades.

Unlock Max Darts x 5 (MB150):
Reach Elite Weapons ranking - Expert 1

Unlock Max Darts x 8 (MB150):
Reach Elite Weapons ranking - Expert 2

Unlock Max Darts x 10 (MB150).
Reach Elite Weapons ranking - Expert 3

Unlock Increased Health:
Reach Survival Specialist ranking - Rating 2

Unlock Dual Wield:
Reach Combat Sharp Shooter ranking - Rating 3

This mission becomes unlocked when you have completed ALL 5 of the Training missions.