Knife Efficiency: Kill four players with melee weapons. 
Explosives Efficiency: Kill four enemies with grenades or explosives. 
AT Efficiency: Kill four vehicles with recoilless rifle. 
Rifle Grenade Efficiency: Kill four enemies with rifle grenades. 
Pistol Efficiency: Kill four enemies with a pistol. 
Rifle Efficiency: Kill four enemies with a semi-automatic rifle. 
SMG Efficiency: Kill four enemies with a submachine gun. 
Sniper Efficiency: Kill four enemies with a scoped rifle.