My Custom Class List:
I have six classes, so I either replace my Mid-range Killer with my Long and Short class depending on my mood.

Russian Mafia
Weapon: AK-74u (Red Dot Sight)
Weapon: M1911
Grenade: Stun
Perk 1: Bandolier
Perk 2: Stopping Power
Perk 3: Steady Aim
Note: I also like using the AK-74u with double tap but only use it when I know I would be playing on a very small map like vacant, wet work, showdown, and shipment where the recoil isn't really a problem.
Mid-range Killer
Weapon: M4 (Red Dot Sight)
Weapon: M1911
Grenade: Stun
Perk 1: Bandolier
Perk 2: Stopping Power
Perk 3: Deep Impact
Note: I chose to use deep impact over steady aim due to the way I use this class. With this class being a mid-range killer, I would want to take the enemy down far away and would also want to kill them quickly as they hide behind cover.
Sneaky Terrorist
Weapon: AK-47 (Silencer)
Weapon: M1911 (Silencer)
Grenade: Flashbang
Perk 1: Bomb Squad
Perk 2: UAV Jammer
Perk 3: Steady Aim
Note: As you can see, I use this as a Ghost class. I use bomb squad to see where hidden claymores are and steady aim to help the AK-47 in CQC. I use a flashbang to help me on escape and evasion because of its huge blast radius compared to the stun. (I make sure the flashbang is right in front of them when I use it)
Sharpshooter
Weapon: M21 (default scope)
Weapon: M1911 (Silencer)
Grenade: Stun
Perk 1: Claymore x2
Perk 2: UAV Jammer
Perk 3: Deep Impact
Note: This is a class I personally love. I use uav jammer over stopping power because I don't want my hiding places to get spotted on radar. I also personally think that there is no need for stopping power because a true sniper would aim from the chest up. I do not aim below the chest so I usually kill a guy with 1-2 shots. (2 shots most of the time for those juggernaut users)

The Janitor
Weapon: W1200 (Grip)
Weapon: M1911
Grenade: Stun
Perk 1: (none)
Perk 2: Sleight of Hand
Perk 3: Steady Aim
Note: This class cleans the room up pretty well!

I don't use extreme conditioning for this class because 1; I don't really run after the target to catch up to and blast him to bits because I'm a bit sneaky when I use this class and 2; I have had it bad for me most of the time when I run up to an enemy. It's either I miss my knife attack or get blasted in the face when someone pops out right in front of me and so all that extra running power would just get me killed even more.

Long and Short
Weapon: G3 (Red Dot Sight)
Weapon: Skorpion (Silencer)
Grenade: Stun
Perk 1: Bandolier
Perk 2: Overkill
Perk 3: Steady Aim
Note: This is my most versatile class. G3 for long range and the Skorpion for those close quarters encounters. Both weapons have almost no recoil and that's why I love this class!