From real architectural offices I am only aware about ArchiCAD 6.5 in combination with Form-Z and Artlantis. ArchiCAD up to version 8 which was released in 2003, and used for a very long time in some offices.
But it depends on what you are planning. In the fields of 2d CAD there are some alternatives. A few of them are really usable: TurboCAD, DenebaCAD, CADintosh, or the early ones like MiniCAD, Professional CAD
If we are talking about 3d modelling, Mac OS 9 was the system to use: Vectorworks, Maya, Blender, Sculpt, Amapi, Canvas, Poser, Bryce, Carrara, or even Combustion, Cinema4D, Strata Studio or Infini-D