Best pizza hands down is Brother's in Telford,PA.
But since I don't get up there too often;DC has alot of decent 'big slice' places that will fill the need,but for taste I'd suggest Palisades Pizzeria & Clam Bar on lower MacArthur or Cappuchino Pizza on Wisc in Georgetown.
__________________
C'dale BBU('05 and '09)/Super Six/Hooligan8and 3,Kona Dew Deluxe,Novara Buzz/Safari,Surly Big Dummy,Marin Pt Reyes,Giant Defy 1,Schwinn DBX SuperSport,Brompton S6L/S2E-X/M6L-X/S12 T Line