Berlin Brandenburger Airport is a smoker-friendly airport. You can smoke before and behind security.
Frankfurt is a great airport for travelers who smoke. Both terminals have plenty smoking areas.
You can certainly smoke at Munich Airport. There are smoking areas available in every gate concourse, from gates A till L.
It is possible to smoke in all three gate areas at Dusseldorf Airport. All travelers have the possibility to smoke behind security.
Hamburg Airport has a smoking area after security. It is sponsored by Lucky Strike and in the middle of the airport.