I don't have enough unlocks yet but I'm quite fond of the
- U-100 MK5
- PSO-1 [4X] (medium range) or HD-33 [1X] (with x2 magnifier) depending on the situation.
- Stubby Grip
- R2 Suppressor
- Starburst Urban Camo
and with "Single" as fire mode.
But i'll probably switch main loadouts as I get more unlocks.