I'm a huge fan of sub sandwiches of all varieties, especially the type usually advertised as "italian". One thing I've come to love is oil and vinegar - whenever it's offered as a condiment in a sandwich shop, I always ask for it.

I'm working on duplicating my favorite sandwiches in my own kitchen, but I'm getting stuck on this - what kinds of oil and vinegar do sandwich shops use? Would it just be olive oil and balsamic, or something else? Are there specific types or varieties that will give me better results?

I understand that this varies by shop (one of my favorite places touts a top-secret proprietary blend of oils), so I'm looking for what types of oil or vinegar are most commonly used by sandwich shops.