Well when I'm playing seriously.. probably Riot Shield with a Stinger because the riot shield makes you invincible to bullets and with a trained trigger finger the stinger can make you invincible to the air force. Perks are Bling Pro because it's got a sweet name. Stopping Power Pro to help stop the enemy's power, and Ninja Pro so they never know when I'm coming.
When I'm just fucking around... M4A1 red dot and Rafficas Akimbo with Scavenger, Stopping Power, and usually steady aim or commando