I mean "working" in that it actually spins around while you're walking with it, not that some cosplayers have made a pioneering breakthrough in medical science.
Cosplay by Kassandra Leigh
This staff, built by Engineer_Corwin, is just incredible. Taking some existing 3D print models made by Jill Cope, he's crammed a motor and complex set of gears in there to create a smooth, consistent spinning effect that looks just like the "real" thing.
See? Not your average "stick with some bits on the end of it".
There are instructions here if you want to try building your own, but be warned, it's some pretty expert-level stuff.