Is adverse yaw ever desirable?
Yes. For deliberate cross control situations, adverse yaw helps.  This means during side slip or forward slip maneuvers, where adverse yaw means less rudder is required to keep the nose pointed in the opposite direction to the lowered wing.  

If you are in a glider or an old classic aircraft with lots of natural adverse yaw, if you lower a wing without any rudder to keep the ball centered, you end up in a mild side slipping turn automatically thanks to adverse yaw.