Anyone know how to instantiate a prefab towards mouse location?

I have a diablo/lol/dota style camera, i have a click to move system and im having a bit of trouble trying to make a script that when i press "1" it shoots a prefab towards my mouse position. Can anyone help me out

 

You need to transform mouse position from screen space into world space.
Have a look at these things in the documentation:
Camera.ScreenToWorldPoint
Input.mousePosition

That will give you a target position then you need to calculate a vector from your current position to the target (direction Vector)
Vector3

Then you need to instantiate your object and apply a force or translation along the direction vector.
Instantiate
Transform.Translate
Rigidbody.AddForce

Get used to looking at the Documentation/Scripting Reference:
http://docs.unity3d.com/Documentation/ScriptReference