The Rex Theatre is one of the neatest bars in Pittsburgh. If you haven't stopped in, make sure you do at some point in the near future. The owners/bartenders are the coolest people, and it's the type of place that welcomes everyone. It's also a great place to hear live music. They have open mic nights on Monday's and shows throughout the week. If you're just going for the drinks, don't worry, because these guys will take care of you at the bar. They aren't stingy on the mixed drinks by any means!
So, do yourself a favor and stop in! You won't regret it!