I agree with Marcelo Rios.
The guy had incredible talent. I have the match he had with Agassi and he was smoking Andre from the baseline. Rios is one of the best shotmakers I've ever seen. For a little guy, he was pretty intimidating too when he was at his best in the late 90's.
Henman and Todd Martin I agree with. But I don't get it with Cedric Pioline. Yes, he made it to two GS finals, but this guy never really struck me as top ten material. He's a good player, but not great (at least not as underratedly great as some fans make him out to be).
I'm a big fan of Alex Corretja, and would've liked it if he won the FO back when Spanish guys like Moya, Bruguera where the ones taking the title. Then again, he did win an ATP Championship, so it's still good.