Favorite restaurant in Pittsburgh is a hole-in-the-wall called Charlie's. It has great crap (crap meaning food that is utterly delicious but absolutely no good for you).
Walls have old concert posters all over. Small, rock or blues always playing.
Favorite Dish Barbeque! Every Wednesday night is Barbeque night after 6. Oh yes, and their french fries are awesome, especially with solent green for dipping.