The most German condiment I can think of (besides Löwensenf, I guess). It’s a mildly spicy, curry-flavored ketchup that you’ll probably find in every single German pantry.

EDIT: actually, now that I think about it, Löwensenf is definitely the classier choice. Traditional spicy German mustard from Düsseldorf. Be careful with the red one, that definitely packs quite a punch (say goodbye to your sinuses), but the others are still very flavorful and well balanced. Goes great with Bratwurst, Leberkäse, or fatty meats (like a pork roast). Some people also like to put it on Teewurst (a type of spreadable smoked sausage made from pork and bacon).

If you don’t like it spicy, they also have a sweet Bavarian style (very mild). Traditionally, this is served with Weißwurst (Bavarian veal sausage) and a pretzel.