I do think a slinky and a yo-yo should be included at that museum. I can still do a few tricks with my yo-yos.
Both the Slinky and the Duncan Yo-Yo are in the Toy Hall of Fame (see my post re: my daughter's social science fair project for why I know this).
The Slinky contains 80 feet of wire and was invented by a man who was trying to come up with a device to cushion a ship's instruments while at sea.
The yo-yo is an ancient toy, dating to at least 500 B.C. My daughter's project included a picture of a toy yo-yo from ancient Greece. The name, "yo-yo" (if I remember correctly), comes from Filipino slang meaning "come-come." In the 1920's, Donald Duncan saw Pedro Flores, a Filipino bellhop, playing with one and selling them. He bought the company, invented the slip-center string that allowed the yo-yo to "sleep," and the fad began.
We've lived the Toy Hall of Fame for the last three months in my house.