Buffy: The Vampire Slayer - Did You Get a Face Job?
If you look at Buffy in Spiral, when she's on top of the RV fighting the knights, watch her. Buffy goes from Sarah to the stunt double then back to Sarah. They even almost show a close up of her stunt double!
Dude, that's basically in 80 percent of the Buffy fight scenes. The stunt doubles for most of the series were very obvious, both face/hair and body wise. It was only in the last one or two seasons where the stunt doubles looked a lot more accurate, but they are still noticeably not Sarah. Same goes for James' stunt double and David's double.
But really, you can't always get a perfect replica of an actor in stunt double form.