Freakin' GSG stealin' my Lazlo's thunder. :cry But seriously, go to Lazlo's. Best pub food in town.
For pizza you should go to Lazzari's and YiaYia's, which are across the street from each other downtown on O Street.
If you've never had Jimmy John's, that's your new favorite sandwich shop. Also downtown.
I've heard good things about Five Guys Burgers at 13th & P, but I've also heard it's expensive for a burger joint.
For Chinese you must go to Panda Garden at 48th & O between Super Saver and Target. Excellent, excellent food. Try the Panda Chicken.