I'm not sure which division you'd stick him in, but James Toney deserves to be mentioned on any chins list.

He's fought opponents ranging from 157-257 pounds, and never been knocked out in the process. He's only had one legit knockdown in his career, which I think happened 17 years ago. The knockdowns against Jones and Peter were both the result of being off-balance, he wasn't hurt in either case.