Visit the NRA range in Fairfax. Nice indoor range to shoot at. 50 yards.
Go to Georgetown and enjoy places to shop and eat. Movie theater. But mostly go for the kayaking/paddle boarding on the Potomac under the bridge.
Visit all of the Smithisonian museums, which are free.
Visit the DC zoo in DuPont, free also.
Rock Creek park for running and bike trails.
So many cool bars to go to in DC and good restaurants too. Speaking of eating, if you want BBQ, go to either Hill Country in Chinatown or Smoke & Barrel in Adams Morgan. The latter had a good selection of bourbon.
Old town in Alexandria is a neat place, especially down by the water. Cool places to eat.
Verizon Center for a Wizards game or if you are in to hockey. FedEx stadium to laugh at the Redskins. Nationals game for a day of baseball.
I use to wor in DC for 5 years. Despite the politics, I loved the city.