Tater tots with BBQ pork on top at See You Tater (CF plaza) and the chicken biscuits at the Virginia biscuit stands. (I forget their names). I have friends who swear by the G (Mike Isabella) sandwiches but I've never had one.
Virginia Country Kitchen (sec 114). My favorite flavor at the See You Tater is the international wok (pork belly, kimchi, onions, cucumbers). The Sandwiches at G (sec 136) are actually really, really good and good sized easy to split for two. Kapnos (sec 301) is also there which is also quite good. Mike Isabella has a restaurant called Catchfly (sec 301) which is Southern food. I hear it is good but haven't tried it yet. I also like Blue Smoke (sec 240). It's far away from my seat, though, so I don't get to go often. It is next to the shake shack and is by the same guy who founded Shake Shack ( I also enjoy a shackburger on occasion).
Other samplings that I have found to be tasty:
Ice cream sandwich at On Rye (Sec 114)
Bahn Mi Dog at Haute Dogs (CF Plaza)
Pinch Dumplings (sec 302)
Italian Sausage burger at Grand Slam Grill (Sec 110 and 141); This was surprisingly good and was spicy if you like that.