Solid Works or Alibre. Depends how much you want to spend and if injection molding is of interest.Follow me on twitter http://twitter.com/mctrivia or my blog at http://4ddice.blogspot.com/
In my opinion I think Rhino 3D is best for precision geometric modeling or ZBrush for high detail character modeling. Ive been using ZBrush for about 10 months now and I dunno what Id do without it.