For a submarine type sandwich, My favorites come from Captain Nemo's of Chicago.
http://www.capnemos.com/index.html
The South Sea and High flier are my favorites.
South Sea:
Ham, Salami, American Cheese, Eggs, Lettuce, Tomato, Onion, and Pineapple Sauce
High Flier:
Ham, Eggs, Turkey Breast, American Cheese, Pickle, Radish, Mustard Sauce, Lettuce Tomato, and Onions
I miss the location over by Wheeling! I haven't had a truly great sub since they closed shop years ago.
Otherwise, If you mean any sandwich, Gyros, Italian Beef, Philly Cheesesteak, Burgers, Chicago Dogs, Corned Beef on Rye, Brats with Sauerkraut, and Polish Sausage are all among my favorites.