SCAR and Feline setups should be most common, and the SCARAB is probably the best of the automatic weapons.
Sights and scopes improve ranged accuracy but does not help so much when someone is in your face. Lasers really improve spray accuracy but cannot be used with a sights and the beam can give away your position. I have a hard time deciding whether to use sights or lasers, not being able to aim down the sight is a bit annoying, but scoping in to shoot at anything accurately isn't as effective in close quarters.