Have you seen... [non-Newtonian fluids]

It's great when nature throws us a curveball.  (E.g., most liquids contract when frozen, but water expands).

Most fluids are "Newtonian", meaning that they continue to behave basically the same way no matter how they are being manipulated (stirred, shaken, flowing in pipes, etc.).  It will always act like we expect it to.

A non-Newtonian fluid, however, can demonstrate unexpected viscosity in certain situations.
Everyday substances found in ketchup, custard, paint, and shampoo can result in non-Newtonian fluids.  In the first video, a simple starch solution on a loudspeaker cone shows how unusually the fluid behaves when disturbed.

Many liquid polymers are non-Newtonian, and also exhibit the Weissenberg effect.  Without going into detail, this effect is that the fluid is not thrown off a spinning rod, but drawn into and across the rod (in this case, going up)!

The Kaye effect is another fluid phenomenon.  In this case, when a viscous fluid like shampoo is poured onto another liquid, something about the surface tension and interaction create a second stream coming up.  Interesting...