Sniper Rifle:
HTI primarily. Can one-shot vehicles in some cases, sounds great and is a trusty friend.
G28. Sounds nice, good stats and it's semi-auto. So it's nice in situations where you need those follow-up shots.
SMG:
The Vector. Only SMG I truly like. Insane RoF, when decked out it's also very accurate. Ran with it as my primary for many hours.
Assault Rifle:
SR3M. I love this thing. Very compact, great damage, high RoF, reloads fast, sounds really cool. Favourite weapon in the game by far.
Famas. Another high RoF weapon, almost half the damage of the SR3M but can equip the 50 round mag. So you can hose people when you need it. Saved my ass plenty of times. The RoF combined with the mag size definitely makes up for the damage.
