Krakatoa is a nice little coffeehouse/sandwich place in Golden Hill (right next to the Turf Club). It's in a cute, little Craftsman-style house with a huge patio shaded by trees. It's a very relaxing place to sit and enjoy some coffee or a light lunch.
It's been a while since I've come here for coffee drinks since I usually go to Calabria, Influx, or Twiggs, but I do stop by Krakatoa when I want a nice sandwich that's inexpensive, but still more interesting than Subway.
I like the Traitor's Head sandwich -- roast beef with cream cheese and horseradish on a fresh Talera bun. It's a nice balance between the savory meat, the creamy cheese, and horseradish kick. I also like the Amboy with peanut butter, banana, and honey (I know I could make this myself, but when laziness strikes...)
My favorite thing about Krakatoa is the potato salad. It might be an odd thing to get excited about, but I really think it's the best potato salad I've had at a restaurant. It looks like just your average American potato salad with potatoes, egg, mayo, and other bits of stuff, but they really hit a magical ratio of ingredients. It's savory with a good onion-y flavor, not too sweet, not overloaded with mayo. It's just right, and that's pretty hard to find these days.