Editor Utility Tool

CreateTool.cs

using UnityEngine;
using UnityEditor;
using System.Collections;

/// <summary>
/// Editor Utility tool.
/// author koki ibukuro
/// </summary>
public class CreateTool : ScriptableObject {
	
	static GameObject _CreateChild (string name)
	{
		GameObject go = new GameObject (name);
		Transform t = go.transform;
		t.parent = Selection.activeTransform;
		t.localScale = Vector3.one;
		t.localPosition = Vector3.zero;
		t.localRotation = Quaternion.identity;
		
		Transform parent = Selection.activeTransform;
		if (parent != null) {
			go.layer = parent.gameObject.layer;
		}
		Selection.activeGameObject = go;
		
		EditorUtility.SetDirty(go);
		return go;
	}
	
	/// <summary>
	/// Create selected object's child. 
	/// SHORTCUT KEY [cmd shift N]
	/// </summary>
	/// <returns>
	/// created gameobject
	/// </returns>
	[MenuItem("Tools/Create/Blank Child %#n")]
	public static GameObject CreateChild ()
	{
		return _CreateChild ("GameObject");
	}
	
	[MenuItem("Tools/Create/Wrap Selected %&n")]
	public static GameObject CreateParent ()
	{
		Transform selected = Selection.activeTransform;
		if(selected == null) {
			return null;
		}
		GameObject parent = _CreateChild (selected.name+"Container");
		Transform t = parent.transform;
		t.parent = selected.parent;
		t.localScale = Vector3.one;
		selected.parent = t;
		return parent;
	}
	
	/// <summary>
	/// Creates 4 poly plane.
	/// </summary>
	/// <returns>
	/// The plane gameobject
	/// </returns>
	[MenuItem ("Tools/Create/Plane")]
	public static GameObject CreatePlane ()
	{
		GameObject go = _CreateChild ("Plane");
		MeshRenderer renderer = go.AddComponent<MeshRenderer> ();
		renderer.castShadows = false;
		renderer.receiveShadows = false;
		
		Mesh mesh = new Mesh ();
		go.AddComponent<MeshFilter> ().sharedMesh = mesh;
		
		// make 4 vertices plane
		Vector3 offset = new Vector3 (-0.5f, -0.5f, 0); // centering offset		
		Vector3[] vertices = new Vector3[4]{new Vector3 (0, 0, 0), new Vector3 (0, 1, 0), new Vector3 (1, 1, 0), new Vector3 (1, 0, 0)};
		
		/*
			
		 1-2
		 |/|
		 0-3
		 
		 */
		for (int i=0; i<vertices.Length; i++) {
			vertices [i] += offset;
		}
		
		mesh.vertices = vertices;
		mesh.uv = new Vector2[4]{new Vector2 (0, 0), new  Vector2 (0, 1), new  Vector2 (1, 1), new Vector2 (1, 0)};
		mesh.triangles = new int [6]{0, 1, 2, 0, 2, 3};
		
		return go;
	}
	
	/// <summary>
	/// Delete all player preferences.
	/// </summary>
	[MenuItem ("Tools/Delete/Delete PlayerPref")]
	public static void DeletePlayerPref ()
	{
		PlayerPrefs.DeleteAll ();
		Debug.LogWarning ("deleted");
	}
	
	
}

Put this script in "Assets/Editor/"