In The Hobbit: An Unexpected Journey, after Bilbo and the Dwarves leave Rivendell they encounter
Three(?) Stone Giants who punch and throw rocks at each other.
It appeared like they were sleeping when all of a sudden they woke up and started battling. They seemed oblivious to presence of the Hobbit and the Dwarves and only focused on hurting each other.
- Why did the Stone Giants fight each other?