Too easy to name YOUR favorite.....but really over time what has been the greatest toy ever.....games are included to make it harder....
Monopoly comes to mind.....The Barbie Doll...Lincoln Logs ( invented by a family member of Frank Lloyd Wright)...Checkers....Cards....
you can go on and on.....
My vote goes to the human mind....back in the day a kid could make a toy out of anything and create his/her toy......