Bun Mee recently opened near my house. Their Vietnamese sandwiches are just spicy enough, with the right amount of filling and at the right price. They also have great salads and sweet potato fries with curry aioli sauce.
I've been having their sandwiches for dinner three times a week for the last month. Highly recommend if you feel like a light (but warm and meaty) sandwich, and you're in the neighborhood (Pacific Heights).
You can also visit their new location downtown on Market Street.