I'll be the good admin and help people out and add some content.
There was an earlier thread about sancwiches with a lot more posts here:
http://www.fairfaxunderground.com/forum/read.php?2,1527
That said, I tried Potbelly Sandwich Works in Fairfax Corner (near the movie thearte) for the first time last night and was pretty impressed. Here's a menu:
