The patterns formed when vibrating a liquid on a speaker cone are standing waves known as Faraday waves. With a large enough amplitude, this produces some very cool effects with a shear-thickening non-Newtonian fluid like oobleck. (It would actually be interesting to see what happens when you vibrate a shear-thinning liquid like shampoo…) This video also details how you can set up this demonstration yourself at home.
Cornstarch Monsters
