James Toney was a master switch hitter. His kos of Nunn, Robinson and Washington came from the southpaw stance and winging a left hook wide across his body.
Wouldn't call them masters, but I think Johnny Bumphus and Jackie Beard switched back and forth a la Hagler, often one round orthodox and the next southpaw.
By far the greatest switch hitter was Bruce Jenner a male who switched into a female.. Now THAT is switch hitting...
Both Greg Page and James Tillis were nice at it, especially Page, who shook Jimmy Young early doing it.