Oh well, I have 6 classes and I use them all (except 2 of them are the same with just two modifications).
Runner 1
Primary: UMP45 with red dot sight
Secondary: Magnum + tactical knife
Equipment: Semtex
Special: Flash Grenade
Perk1: Marathon PRO
Perk2: Lightweight PRO
Perk3: Commando PRO
Deathstreak: Martyrdom
Runner 2
More tactical version of Runner 1. Differences are:
Primary weapon: UMP45 with silencer
Perk3: Ninja PRO.
Sniper
Primary: Intervention with heartbeat sensor
Secondary: G18 Akimbo
Equipment: Claymores
Special: Smoke Grenade
Perk1: Sleight of Hand PRO
Perk2: Stopping Power PRO
Perk3: Commando PRO
Deathstreak: Final Stand
Assault class
Primary: ACR with red dot sight and grenade launcher
Secondary: Spas-12 with grip and fmj
Equipment: Semtex
Special: Stun Grenade
Perk1: Scavenger PRO
Perk2: Stopping Power PRO
Perk3: Commando PRO
Deathstreak: Final Stand
Lame class
Primary: F2000 with grenade launcher
Secondary: Thumper
Equipment: Semtex
Special: Stun Grenade
Perk1: Sleight of Hand PRO
Perk2: Danger Close PRO
Perk3: Commando PRO
Deathstreak: Martyrdom
For the killstreaks, I'm always going for harrier>chopper gunner>nuke. Sometimes I change it, sometimes.
I also have lmg+stinger class, but it's lame and not interesting xd
I usually go for smg class.
And after prestiging, I'm gonna change my classes I guess.