Currywurst. Chopped fried or grilled sausage with ketchup and curry spice sprinkled on top. Often served with fries.
You can get it almost everywhere in Germany, especially at street festivals. Simple, absolutely unhealthy and delicious.
Edit: I would also have said the Döner Kebab. Veil or chicken grilled on a vertical spitroast, sliced into thin strands of meat, loaded into a slightly toasted flatbread along with lettuce, tomatoes, cucumber, onions and depending on the region and restaurant white or red cabbage in vinegar and oil, together with a yogurt sauce.
But you could argue that Döner is Turkish because it was invented by a Turkish immigrant and is usually prepared by Turkish descendants (or those who look Turkish). But then again I heard that restaurants in Turkey started offering German Döner because that's what tourists expected to get.
Turkish immigrants didn't invent döner. They changed the ingredients a little according to local people's tastes. Döner dates back hundred of years back. Döner is Turkish, no one can argue about that. However you can call your version of döner local food of your country. Same logic goes for pizza, origin of it is Italian (maybe Greek idk) but there is American pizza.
I have never seen a German version of döner here in Turkey. I guess you can find it in some really busy touristic places.