I've been using a new class and love it lately. Vector w/ rapid fire, USB w/ FMJ (at like 60ish kills just trying to get tactical), throwing knife, stun, Marathon, Stopping power, Commando
I'm getting crazy good at throwing knives now and it's made the game a lot more fun. Just got a game ending kill cam where I found 2 guys at the sniper cliff on Afghan at 7300, threw a throwing knife at one and sprinted at the other and stabbed him and got a double kill off it. It took about a week where I was terrible with them but once you get the hang of it it's awesome for conserving ammo and just flat out owning the fuck out of people.