I've been to a couple of Tyler Cowen's "SOME PLACES YOU MUST TRY" list:
Hong Kong Palace- this place is incredible. Always packed. Get the lamb with cumin.
Horace & Dickie’s Seafood Carryout- I don't share Cowen's enthusiasm for Horace & Dickie's but then again I am not such a fried fish fan. The Macaroni is mediocre, the Collard Greens are average. It definitely has character, though. Surprisingly, D.C. does not have a good offering of reasonably priced soul food. Georgia Brown's, which is a good deal more expensive is supposed to be quite good. Though Georgia Brown's is really a higher end low country cuisine place. I have also heard good things about the Florida Avenue Grill.
Shamshiry- This place always hits the spot. Persian food is simple and a bit bland, but tasty nonetheless.
Fogo de Chao- Don't eat for days in anticipation. Fogo de Chao is a massive meat orgy. The salad bar alone is worth it. This place is simply excellent.