My favourite class:
Intervention - either with acog, or extended mags
akimbo magnums
Sleight of hand pro (the pro part being the key, scoping in quicker while sniping is very useful)
Stopping power pro
Ninja pro/commando pro/steady aim pro depending on the game type
I'm currently working on getting all the prestige related intervention titles and emblems. Meaning I haven't used any other gun in a long time, as it takes frickin ages. Getting close though. While some of the normal titles/emblems look cool, I wanna get some that actually take a lot of effort to get. As of yet I haven't seen anyone else with the emblem I have. 2500 kills with the intervention takes a fair while, not to mention all the headshots. Getting close though, up to about 2000 intervention kills on this current prestige.
Another of my favourite classes:
Any primary
1887 shotgun akimbo
Seriously the 1887 is preposterously good when akimbo. The range is INSANE for a shotgun. Only reason I don't use them more is because they're unlocked level 67. If I wanna carry on prestiging I won't get to use them that often.
Oh yeah, another class which is great for the lulz:
Any smg
Magnum with tactical knife
Marathon pro
lightweight pro
commando pro
Then just switch to your tactical knife magnum and play games without firing a shot, only knifing people. The lunge distance with commando pro is pretty hilarious, plus the tactical knife means the stabbing animation is a lot quicker (great if theres 2-3 guys).