Le Caprice, the nice French bakery at 3460 14th Street NW, has a lot of good (and reasonably priced) baked goods. However, they also have delicious breakfast sandwiches. A lot recently I've been stopping by to get the breakfast combo, of which there are about 4 -- sandwich, coffee and a little cup of fruit for about $7. My favorite is the one with tasty roll -- it's egg, some kind of delicious cheese and a slice of tomato. Simple but good. You can add meat too, but it's not necessary, still delicious.
They've also got a bunch of premade lunch sandwiches on various kinds of bread (see below), which I haven't checked out yet, but based on the breakfast ones are probably pretty delicious.
And considering the nice weather lately (finally) it's a nice spot to get breakfast and sit on the patio.