Culux (Curry Deluxe), on Rudolfplatz. Currywurst is practically a German national dish, but the relationship to what any english person knows as "curry", i.e. indian food, is slight. It's simply a sausage with a basic, spicy, ketchup-like sauce made from curry powder. Usually served as a take-away snack on a small paper plate, maybe with chips (pommes), to be eaten on the street with a two-pronged, plastic fork. Being a food, and especially curry, snob I steered well clear of this particular food for a long time.
However, I had my first ever Currywurst in Culux a few weeks ago, on the recommendation of a friend, and it has got me hooked. Basically, you mix and match the sausage, sauce flavour and hotness, and style and topping of your chips to create your ideal snack meal. The sausages, as with all german ones, are large, meaty and tasty, and there is a good variety to choose from (Bratwurst to Chorizo to Tofu). The sauce is still basic, but actually pretty good, again with a wide variety of flavours. The chips are hot and fresh and crispy and generally excellent. You can have your currywurst topping anywhere from mild to super-, mega-, or ultra- spicy (which comes with an age limit and a disclaimer of responsibility for the effects on your health). Personally, I'll stick in the middle with just "hot", I'm not looking to impress anyone. The staff are cheerful and friendly too, which is always a plus.