Alright. I play on PS3 and primarily snipe (around a 5KD when I run around and quick scope), but I can use assault rifles (1.5 KD), and SMGs (3KD). Stay away from riot shields...
So, here are some good setups with some of my favorite guns:
Assault Rifle: Tar-21, Scar-H, or AK-47 (attachment: SILENCER/FMJ, the best attachments. Sights: Waste. Noob Tube: Unfair. Shotgun/HB Sensor: Useless)
Secondaries: (Spas, AA-12, M1014, Raffica, G-18, PP2000)
(CHOOSE ONE OF EACH FROM ABOVE AND USE THESE PERKS/KS/etc. VVV)
Equiptment: Claymore or Semtex or Frag (I prefer claymore)
First Perk: Scavenger (allows for resupplies often)
Second Perk: Stopping Power (Not a must for the guns I listed, but 3 shot/4 shot kills make the gun uber.)
Third Perk: Ninja (Invisible to HBS, If you have pro, silent footsteps, and is good combo with silencer)
Death Streak: None (Only for if you are horrific at the game)
Those are my preffered assault rifles and perks, but I also like the ACR with Sleight of Hand, Stopping power, and steady aim. ACR is also nice.
SMGS: UMP. Marathon, Lightweight, Ninja. Use a shotgun. Nuff said.
Sniping: If you have a PS3, I could help you get better b/c sniping is oneshot kill and amazing if you become amazing.
Just PM me for more in-depth tips, b/c i need to sleep.
Hope this helps