Jarlsberg is my absolute favourite cheese. It's a Norwegian swiss cheese and goes great with pickles (although you probably don't want pickle-breath after lunch). I also agree with coffeesp00ns about Manchego. Seriously delicious stuff. Those were my two favourite cheeses when I worked at a German deli. Some other good/popular ones are havarti (especially horseradish and chive havarti (goes great with roast beef)), buttercheese (if American cheese is the standard in America, buttercheese is the standard in Germany), and gouda (aged or smoked (although I'm really not a fan of smoked gouda)).
Hmm, just looked up butter cheese. I guess in the U.S. it's referred to as "butterkase" which makes sense, since it's a German thing. I haven't had havarti in a while. Good one, thanks! Haven't eaten much Jarlsberg, but I'm willing to give it a shot. A sandwich needs a pickle sometimes.