Cornstarch + Mr Scruff from Bek on Vimeo.
Here is a very standard showing of how the non Newtonian fluids work.

Dancing Speaker - Non Newtonian Fluid from Nico Weinmann on Vimeo.

This here is my first inspiration of my exam prep. The theme was 'Force' and it was difficult till I saw this. Non Newtonian fluids which are liquid normally but solid under the force of the bass.