1. Water: Water has a relatively low viscosity, meaning it flows easily. This is why it is used in many applications where a fluid needs to move quickly, such as in plumbing and irrigation.

2. Acetone: Acetone is a solvent that has a very low viscosity, making it ideal for thinning paints and varnishes. It also evaporates quickly, making it useful for cleaning purposes.

Let me know if you'd like to know more about viscosity or other low viscosity substances!