Banter. They always have a comeback.
Often under the radar. Oftentimes I get the feeling they are testing for connections by seeing who really gets what their humor is about.
One INFJ I knew was very sarcastic. Not mean, mind you, but her humor was very dry. The way to her heart was to be Bill Murray.
Another INFJ I knew was very sharp and intelligent, but had perpetual blond moments (to the point where I wonder if she played them up a bit). She would say just the silliest things, such as "Hey Udog, how far do you live from your home?", and then laugh uncontrollably when everyone starts joking with her about it.