Depends on your definition - there's so few, that they've pretty much fought each other, at least twice. Sonya Lamonakis is pretty popular; not exactly nice to look at, but lots of fun to watch.
SMW Ragozina fought a HW belt holder (still weighing SMW) and KO'd her. That was 2 years ago now though. Laila Ali ducked Ragozina, as she did others.
according to boxrec its Ijeoma Egbunine This content is protected [url]http://boxrec.com/list_bouts.php?human_id=283352&cat=boxer[/url]