Depends on your style/preferences
Carbine: Slower fire rate, high damage, precise both when in hip fire and when aiming
G36: Higher Fire Rate, slower fire rate compared to the Carbine, precise when aiming, hip fire not so precise
LSGM3: In a sentece, good DMG per second,
I advise you to check Chrono's charts and get your hands on this weapons and give it a try