I think this is a fairly straightforward example from The Legend of Zelda: The Wind Waker: Link and Zelda◊ fighting Ganondorf. There's also Inuyasha and Kagome: 1◊, 2◊. And Susan, Peter, and Edmund from The Lion, the Witch, and the Wardrobe. 1◊, 2◊. I'm sure it would be possible to find more.