What is a Non-Newtonian Fluid? Well, the Wikipedia summary is pretty thorough, but if you don't like clicking things, they're basically fluids whose viscosity is dependent on the shear rate. Even more basically, think things like ketchup or toothpaste or Silly Putty or whipped cream.
Anyways, watching it bounce around on a speaker is surreal and kinda magical. Just skip to around the 1:40 mark if you wanna skip the talking and get straight to the weird bouncing liquid that don't abide by Newton's rules: