Though not as strictly enforced as the rules concerning hot dogs, there are certain guidelines for Italian subs that most of the best delis in Chicago follow. Basically, thinly sliced cured meats, oil and vinegar dressing, and giardiniera are good; mayonnaise is bad. One of my favorites is the Alpine Sub ($5.25) at Alpine Food Shop in Elmwood Park, which keeps things simple with a mix of ham, salami, capocollo, and provolone (only some crustier bread would improve it). I'd never consider adding anything else, for fear of throwing off the balance or unwittingly offending the owners. But leave it to a local to show me that sometimes modifications aren't such a bad thing.
Jeff Mauro (host of the Food Network's Sandwich King and $24 in 24), grew up in the nearby western suburb, and when we decided to do a tour of some of his favorite local spots, he made sure that Alpine on the list. Though he admires the simplicity of the original, he occasionally likes to add some roasted red peppers and portabella mushrooms to the mix. He got the idea after his wife kept ordering the veggie sandwich. Realizing it was actually good (something I also discovered during my initial visit), he decided to combine the forces of the two subs. The result has all the salty, funky meats you want from an Italian sub, with some sweetness and extra juiciness. Not an improvement on the original, but a great alternative if you're looking to change things up.