The two classes I use the most are these two.
First Class

Rape
M4A1-Noobtube attached
Perks
One man Army Pro
Danger Close Pro
Scrambler Pro

Second Class
Nuke
M16A1-Red dot eye
Moddles 1887
Scavenger Pro
Stopping Power Pro
Ninja Pro

Kill streak
Harrier Strike
Chopper Gunner
Nuke