Most people have made oobleck at some point in their school career, whether it was in elementary school as a fun project or in high school to demonstrate physical properties.
How did oobleck get its name? From the Dr. Seuss book Bartholomew and the Oobleck.
This simple, non-Newtonian fluid made from a mix of cornstarch and water defies Newton's Law of Viscosity. Oobleck magically transforms (well, not magically, but it seems like it!) from a liquid to a solid with the slap of a hand, punch of a fist, or kick of a foot. Because of the shear-thickening behavior of oobleck, a greater applied force leads to a greater resisting force from the fluid and it behaving like a solid. Without an applied force, the oobleck will behave like a liquid. The behaviors of these shear-thickening fluids allow them to be used as body armor since they offer great flexibility and ease of movement, but would resist a sudden force such as a bullet or knife.
Watch this video if you've ever wondered how to walk on a liquid: