Ok I am going to admit this. There is one map that I hate, Skidrow , but I have a very good strategy for.
UMP .45 /silenced
Scavenger Pro
Stopping Power Pro
Ninja Pro
Basically there is this elevated room on Skidrow, complete with a kitchen, the other room has a HUGE hole in the wall and a small window. There are only two entry points into this room, and claymore them both. (staircases). Then I go back into the room and shoot people as they run up and down the hallway or across the courtyard. The claymores get about half of my kills, even if someone has scrambler, the click gives me time to turn around and shoot them as they come into the room.
This is the ONLY map I use a camping strategy on. But it works amazingly well.
On all other maps my strategy is to rush, I play FFA only, for that I use:
UMP .45 Silenced
Marathon Pro
Lightweight Pro
Ninja Pro
Killsteaks currently are Missle, Harrier, Gunner.