Ali, Patterson, Ward, Whitaker, Pep, Toney, Graham, Eubank, Leonard, Robinson, Locche, Hopkins, Roy Jones Jr,...etc...
Ali, without a doubt. Muhammad Ali was a heavyweight. How a heavyweight ever moved like that still makes no sense to me.
No love for Rigondeaux? Also...perhaps not "slick" but Tyson was elusive in his early days with his head movement.
:deal, I'd like to say Pep as well but honestly despite knowing his history I've never seen enough footage of him to really be able to gage his slickness. His resume isn't deep enough (number of fights) yet to consider him