That or baseball. As George Carlin says, baseball is a peaceful game. 
College football sure isn't!
Once, on New Year's Day, the couple who are my parents' best friends came to watch the bowl games with our family, and there was a history of "friendly rivalry" between our families-we'd root for opposing teams. Unfortunately, that year it got to be unfriendly-it evolved into a shouting match between the wife and my brother, and he picked up a chair and threw it at the door, making a hole in it. My brother was punished, but everyone agreed that the rivalry had gone too far and it's since been toned down.
On the other hand, this couple and my parents have totally opposite political leanings...
Sometimes I have to wonder what they find to talk about that makes them best friends.