Just post your favourite classes
At the moment I like:
G3 Silenced (Red Tiger)
M9
Stun
Bandolier
Stopping Power
Steady Aim
I find this class useful in most situations because it's accurate from hip, has good damage and range, can be controlled easily and I can fire it quickly (fast fingers ftw!). The silencer is there because the Iron Sights are easy to handle, and it benefits from it for flanking etc.
The only thing I have against this class is the knife bug. If you lunge with the knife, it doesn't always count it.