Gotta add some rather unique guns. no pics because I'm on my phone, sorry.
HK417 w/ 16" barrel
-Can be used as both a DMR and an assault rifle.
-Low ROF, high damage, high recoil but highly accurate for first few shots.
AEK973
-High damage but with relatively low accuracy
-High RPM for an assault rifle, recoil mechanism makes it very manageable.
MP5K/10 PDW
-Basically a custom MP5K PDW (you can find a pic on Wikipedia) chambered in 10mm Auto.
-Normal RPM, lower capacity, high recoil
-Very powerful
-Sleek nickel finish on metal parts
MSMC
-Fires larger 5.56mm PDW rounds.
-Higher damage than most PDWs but at the expense of higher recoil
M4A1 CQBR .50 Beowulf
-Compact assault rifle with a .50 Beowulf upper reciever.
-High recoil and low accuracy, but magnum-level damage.
-Extra damage against vehicles.
AK12 Grendel
-Moderately-high damage and recoil
-Good accuracy
-Can fire full auto or in a 3-round burst with a single click. (Some weird sequencing could go on here.)
Smith and Wesson Model 500
-Extremely high damage revolver.
-Very high recoil, slow recovery time.
EDIT: OH YEAH HOW COULD I FORGET
AK-9 Silenced
-Lower RPM than AS Val, but with higher accuracy and lower recoil.
-High damage at close range, armor piercing.
-Looks loving sick.