Front attachment
4 muzzle break
6 muzzle break
silencer
Under the barrel attachment
gun sling
grip
Scope
upgraded iron sight
COGA (like the Acog from COD)
Yeotek red dot (square one)
D-flex red dot (the arc shaped one)
C-U-Gone red dot (circle shaped one)
Snoop-R (Sniper scope)
Greeneye-spec ops scope
Magazines
Duct tape- quick reload every other reload
High capacity- larger mag
Drum mag- even larger
Double Drum mag- even larger than that!
That enought choices for you mate?