There's not really anything other than chains in Tysons. You have Coastal Flats at the mall and a few other bars on the third floor. Also, there's Chics N Wings on rt 7 near the mall, but they don't have a large selection.
I strongly recommend going into Arlington if you don't mind the 20 minute drive + traffic. You need to go to Galaxy Hut. They have by far the biggest selection of beers on tap in the area, but it's a dive and some what small. Other than that it's amazing.
Beyond that, stick to Falls Church. There's a nice Irish Pub on rte 7 called Ireland's Four Provinces. Plus, you can go into Ballston, which might have a few more options, but I'm not as familar with the Arlington scene.
I hope that helps. Bottomline, if you're staying in Tysons, go to Chics N Wings or Coastal Flats. If you don't mind the drive, definitely go to Galaxy Hut.