If you know how to aim down your sights, the AEK is your Operation Swordbreaker. It dominates so much.
If you like to win every gunfight, use a 200 round light machine gun with supression and keep firing on your enemy at all times.
If sniping, use no scope for semi-snipers and supression for bolt action.
If engineer, use the M4. Very accurate. Laser sight just adds to your mini automatic sniper rifle machine gun. Rocket launchers make you a walking threat. Use explosive as your specialization.
Medic: AEK, B93R, M320 grenade launcher, frag specialization. The all around walking TANK.