Make a generic popup selection field.

	// Creates an instance of a primitive depending on the option selected by the user.
	
	class EditorGUILayoutPopup extends EditorWindow {
		var options : String[] = ["Cube", "Sphere", "Plane"];
		var index : int = 0;
		
		@MenuItem("Examples/Editor GUILayout Popup usage")
		static function Init() {
			var window = GetWindow(EditorGUILayoutPopup);
			window.Show();
		}
		function OnGUI() {
			index = EditorGUILayout.Popup(index, options);
			if(GUILayout.Button("Create"))
				InstantiatePrimitive();
		}
		function InstantiatePrimitive() {
			switch (index) {
				case 0:
					var cube : GameObject  = GameObject.CreatePrimitive(PrimitiveType.Cube);
	   				cube.transform.position = Vector3.zero;
	   				break;
				case 1:
					 var sphere : GameObject = GameObject.CreatePrimitive(PrimitiveType.Sphere);
					sphere.transform.position = Vector3.zero;
					break;
				case 2:
					var plane : GameObject = GameObject.CreatePrimitive(PrimitiveType.Plane);
					plane.transform.position = Vector3.zero;
					break;
				default:
					Debug.LogError("Unrecognized Option");
					break;
			}
		}
	}