I think I'm gonna have to go with banter as my favourite, too! (why I then made a comic where half the characters have difficulties communicating is anyone's guess). Actual arguments are a fun challenge, but I think my favourite is when characters begin to get comfortable enough to tease and pick on each other or get on each other's case a little more. ~FRIENDSHIP!!~
As for genre, my favourite is some kind of fantasy. The part of storytelling that's interesting to me is exploring people, and I think that sometimes reality can get in the way of that, in a way? To me fantasy means you don't have to be distracted by recognising the place or the time or the society that these characters are supposed to be in... and can hopefully just see them as people.