AR's: Famas, F200. Famas<M16A4 F200=shittest recoil. FAL isn't bad in the right hands.
SMG's: MP5K, UMP is better. P90, too much recoil. Mini Uzi, same issue. Vector, same scenario as FAL.
LMG's: ALL. I hate them, too much recoil, not worth using bling for Grip+Sight.
Sniper's: None. All have their pros and cons. Least fave is 50. too much recoil and Barret Bashers put me off.
Riot Shield: Useless load of crap.
All the attatchmetns are fine, as long as they aren't abused. IE; Mara,LW and Comm with a TK.
Thermal is fine. Amazing on AR's. Also becomes a standard sniper scope when EMP'd.