Terminal was a great map on MW2, however I don't like it when they make the same map on another COD. It seems to me like they run out of map ideas when this happens.
Forgot about Rust as well. That map got mental on hardcore Headquarters. You could just sit at the top of the map with an LMG and get an easy nuke haha.
Shipment and Showdown are probably my favorites. Some of the WaW maps were sick too. There was a map in Cod2 super similar to wasteland, I liked it a bit better. I'm not sure if it was an intentional remake or not.