Forget Subway and Quiznos, you gotta try Bay Cities in Santa Monica! The are often crowded at peak times, but it you have some time, it worth checking out. Walk through the aisles of a great selection of gourmet foods and drinks. I heard they bake all day long, so your breads and baked goods will be fresh! It's not cheap, so don't expect fast-food prices. If you really must grab and go, they prepare popular sandwiches during rush hour at the front counter, so you can literally just grab, pay and go!
Oh, if you like olives, they have a great selection of those, too. It's a yummy, yummy place!