I dont have all the weapons yet as some of those elusive ultra rares just wont drop for me. But in general i would say N7 Hurricane is one the best pistols in game for straight up damage dealing. If you are using a lightweight character id go with that or equalizer as very good lower weight guns. Some people like the Talon as well as the kind of mini shotgun for close range.
Assault rifles i keep find myself coming back to Cyclone as a good all-around weapon with reasonable weight. as some mentioed X5-Ghost is solid as well. Revenant works good on turbocharge soldiers if you can get the stability/accuracy up. Thokin is fun as well and should not be hard to get
Snipers - black widow and vanquisher are both good choices.
Shotguns - i dont use as much so my options here are not as tested but i like Dhan, Pirhana, Hesh. Fun factor i go with Reegar Carbine.
There are a lot of garbage weapons in the game which is sad because i want them to feel better. If you run Mattock or Halberd you on higher than silver you will be frustrated. it just takes too long to kill and your hands will hurt when you are done from mashing the trigger so many times. if you cant get headshots those guns lose a lot of their power.