Early in "The Perfect Mate," a Ferengi, Par Lenor, accosts Captain Picard and Ambassador Briam. One of the quips of Lenor is that
Peace is good for trade---unless you happen to be an arms merchant
After a few seconds, Captain Picard smiles and walks away with the ambassador. It seems as though Picard is smiling because he finds the joke funny.
I wonder if this is a goof by Patrick Stewart. Picard is normally stoic, and though he does smile, you'd think that smiling at a joke made by a Ferengi would not be high on his list of things to do.
Though it is possible that the script has Picard smiling. He's not a robot, after all.