Adds "Create > Editor Script" menu to scripts a right click that automatically creates editor scripts.

CreateEditorScriptMenuItem.cs

using System;
using System.Globalization;
using System.Text;
using System.IO;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;
using UnityEditor.ProjectWindowCallback;

public static class CreateEditorScriptMenuItem {
	const string fileNameTemplate = "{0}Editor.cs";
	const string template = "using UnityEngine;\nusing UnityEditor;\n\n[CustomEditor(typeof({0}))]\npublic class {0}Editor : Editor {{\n\tpublic override void OnInspectorGUI () {{\n\t\tbase.OnInspectorGUI();\n\t}}\n}}";

	[MenuItem("Assets/Create/Editor Script", true)]
	public static bool CreateEditorScriptValidator () {
		if (Selection.activeObject == null || !(Selection.activeObject is MonoScript)) return false;
		var typeName = Selection.activeObject.name;
		string fileName = string.Format(fileNameTemplate, typeName);
		var directoryPath = Path.GetDirectoryName(AssetDatabase.GetAssetPath(Selection.activeObject));
		string path = directoryPath+"/Editor/"+fileName;
		var asset = AssetDatabase.LoadAssetAtPath<Object>(path);
		return asset == null;
	}

	[MenuItem("Assets/Create/Editor Script", false, 81)]
	public static void CreateEditorScript () {
		var typeName = Selection.activeObject.name;
		var directoryPath = Path.GetDirectoryName(AssetDatabase.GetAssetPath(Selection.activeObject));
		var targetDirectoryPath = directoryPath+"/Editor";
		if(!AssetDatabase.GetSubFolders(directoryPath).Contains(targetDirectoryPath)) {
			AssetDatabase.CreateFolder(directoryPath, "Editor");
			AssetDatabase.LoadAssetAtPath<DefaultAsset>(targetDirectoryPath);
		}
			
		string fileName = string.Format(fileNameTemplate, typeName);
		string contents = string.Format(template, typeName);
		string filePath = AssetDatabase.GenerateUniqueAssetPath(Path.Combine(targetDirectoryPath, fileName));
	    ScriptAssetCreator.CreateNewFile(filePath, contents);
	}
}



public static class ScriptAssetCreator {
	public static void CreateNewFile (string filePath, string text) {
		CreateScriptAssetFromTemplate(filePath, text);
	}
    public static void CreateNewFileAndStartNameEditing (string filePath, string text) {
		ProjectWindowUtil.StartNameEditingIfProjectWindowExists(0, ScriptableObject.CreateInstance<CreateScriptAssetAction>(), filePath, null, text);
	}

    public static UnityEngine.Object CreateScriptAssetFromTemplate(string filePath, string text) {
        string fullPath = Path.GetFullPath(filePath);
        UTF8Encoding encoding = new UTF8Encoding(true, false);
        bool append = false;
        StreamWriter streamWriter = new StreamWriter(fullPath, append, encoding);
        streamWriter.Write(text);
        streamWriter.Close();
        AssetDatabase.ImportAsset(filePath);
        return AssetDatabase.LoadAssetAtPath(filePath, typeof(DefaultAsset));
    }

	class CreateScriptAssetAction : EndNameEditAction {
		public override void Action(int instanceId, string filePath, string text) {
			UnityEngine.Object asset = CreateScriptAssetFromTemplate(filePath, text);
			ProjectWindowUtil.ShowCreatedAsset(asset);
		}	
	}
    
    // Gets a camelCase variable name from a string
    public static string ToCamelCase(string text) {
        List<char> outputList = new List<char>();
        char[] a = text.ToLower().ToCharArray();
        for (int i = 0; i < a.Length; i++) {
            if(a[i] == ' ') continue;
            if(i == 0) outputList.Add(char.ToLower(a[i]));
            else if(a[i-1] == ' ') outputList.Add(char.ToUpper(a[i]));
            else outputList.Add(a[i]);
        }
        return new string(outputList.ToArray());
    }
}

Cool gist What/where is ScriptAssetCreator ?

Oh well noticed! I've updated it. Not tested though!

Thanks!