Either FAD with RDS and Muzzle Flash Suppressor or ARX with Underbarrel Shotty and Silencer
K7 with Grip/Rapid Fire
ARX-160 with Grip/Tracker Sight
I've used the MSBS (with full-auto attachment), the Chain SAW, the AK-12, the ARX-160 and every Marksman rifle (without the sniper scope). My favorite is probably the SVU or the MK14 EBR. Oh and the Chain SAW.