Winky Wright
Vitali Klitschko
Ike Ibeabuchi
Joe Calzaghe
Jermain Taylor
Arthur Abraham
Floyd Mayweather Jr.
Ricky Hatton
Juan Manuel Marquez

I'm sure that there are more...but those are the only ones that really click right off the button for me as fighters that have never been knocked out...some of those have'nt been downed either.