How to I make something like in conterstrike source "spray" thing?

I need something like a texture applier on a geometry on mouse click (something like texture on texture)

Alright, first you need to have a prefab of the projector you want to place.

The, you make a public GameObject variable in the script you’re going to be using to create the projector (we’ll call it myProjector) as well as a public Camera variable for the camera object (myCamera).

When you want to create the projector, do this:

GameObject newProjector = Instantiate(myProjector, myCamera.transform.position, myCamera.transform.rotation);

This creates a duplicate of the projector prefab and places it in the same place as the camera.