If you're asking for advice I'd recommend the MP7 and P90 for submachine guns, Scar, ACR, and Type 95 for assault rifles, L118A and Barret for snipers, and Striker, Usas-12, and Spas-12 for shotguns. None of them require sights.
For submachine guns I'd recommend a silencer and rapidfire or extended mags, silencer and extended mags for the first two assault rifles I mentioned and a silencer and rapid fire for the Type 95. I usually use extended mags and the speed or stability proficiency on snipers, and for shotguns damage and extended mags.
