In reply to Toerag: to me the Quarryman is a groove/narrow corner, a Chimney needs to be more parallel-sided. As stated above, Gin palace doesn't count 'cos the crux isn't the chimney.
Offwidths like Ray's roof don't count, you can fit your whole body into a chimney.
Aside from the good suggestions above, what would constitute a super hard chimney? Slick rock? A shallow chimney in a horizontal roof where you're fighting not to fall out sideways? Something wide like Devil's tower in Wyoming which you bridge, or something constrictive?