I don't think the silver/ruby slippers really belong on this page. While yes, they have teleportation powers, they don't get used until the final moments of the story. They do not provide a power that Dorothy has access to throughout the story, unless you count "staying on permanently and keeping her from washing her feet" as a power. And in the book, the cap controlling the flying monkeys is basically a short-term item, again, not something she has throughout her stay which gives her an advantage in her adventures.