even konopke is still my personal favorite, but i discovered (got a tip from a friend who is an upper class restaurant owner) a great '2nd' place.
u-bahnhof gesundbrunnen in berlin, wedding is a place called "curry baude", right next to the station entrance oposite the shopping center, they produce their own sausage and make also really good pommes frites... not a greasy and smelly place and good tasty ketchup, too
well worth a try, if you dig that kind of street food.
GAFM ***