Commander Vander... despite his age and all the critics, he's still a decent proffesional fighter which speaks volumes about the man's physical conditioning. He's not getting whacked out by the kinds of bums that Tyson got destroyed by just yet.
Ibeabuchi and Golota are great shouts. There's always the chance that Foreman, Hopkins etc would start feeling sorry for you after giving you a beat-down ... Golota would probably rip out your liver and eat it, then start drawing pictures of clowns on the wall with your blood.
McCall and mercer deserve some mention for active guys - mccall's still in great shape and you couldn't hurt him with a 2 x 4. Mercer can still ko 300 lb men apparently