Brandeezy
Superstar
I used that one for a bit, but then when back to my silenced pew-pew sniper
I actually just unlocked the 'base' weapon for that gun, but haven't seen what attachments it has. you unlock a bunch of guns when you get to the second island (meaning when your missions actually take you there). the difficulty of the baddies also steps up on the 2nd island
The Heavy dudes are I swear there's 2-3 of them in every mission there. They eat bullets like lunch