Make a 3D Button.

This works like a normal GUI.Button, but it has a 3D position and is drawn by a handle function

Note: Use HandleUtility.GetHandleSize where you might want to have constant screen-sized handles.

Button Handle as a rectangle in the Scene View.

	// Create a simple button on 3D space and when the user clicks over the handle
	// it prints a message.
	
	@CustomEditor (ButtonChecker)
	class ButtonHandle extends Editor {
		function OnSceneGUI () {
	        target.checkButton = 
	        	Handles.Button(target.transform.position + Vector3(0,2,0),
	        			Quaternion.identity,
	        			3,
	        			3,
	        			Handles.DrawRectangle);	
	    }
	}

And the script attached to this handle:

	// Usage: Place this script on the object you want to create the button on.
	// When the script is placed, just press "Play" and click the rectangle
	// that appears over the GameObject
	
	var checkButton : boolean = true;
	
	function Update() {
		if(checkButton)
			Debug.Log("The handle button has been pressed!");
	}