Liquids:
* Water: The most obvious answer!
* Other Liquids: Rain, coffee, juice, oil, lotion
Actions:
* Spraying: Using a spray bottle or hose to apply liquid.
* Pouring: Pouring a liquid substance on something.
* Soaking: Submerging something in a liquid.
Indirectly:
* Humidity: Increasing the amount of water vapor in the air.
* Melting Ice/Snow: Solid water turning into liquid water.
* Condensation: Water vapor turning into liquid water on a surface.
To give you a more specific answer, what did you have in mind when you asked the question? Are you trying to wet something in particular?