Selections.cs

using System.Linq;
using UnityEditor;
using UnityEngine;

namespace Gubbins.Editor
{
    public class Selections
    {
        [MenuItem("Tools/Gubbins/Selections/Objects with Missing Scripts")]
        public static void SelectMissing()
        {
            Selection.objects = Object.FindObjectsOfType<Transform>()
                .Where(t => t.GetComponents<Component>()
                    .Any(c => c == null))
                .Select(t => t.gameObject as Object)
                .ToArray();
        }

        public static void SelectObjectsWith<T>() where T : Component
        {
            Selection.objects = Object.FindObjectsOfType<Transform>()
                .Where(t => t.GetComponent<T>() != null)
                .Select(t => t.gameObject as Object)
                .ToArray();
        }

        [MenuItem("Tools/Gubbins/Selections/Objects with Selected Component")]
        private static void SelectWithComponent()
        {
            var ms = Selection.activeObject as MonoScript;
            var type = ms.GetClass();

            if (!type.IsSubclassOf(typeof(Component))) return;

            var method = typeof(Selections).GetMethod("SelectObjectsWith");
            var typeMethod = method.MakeGenericMethod(type);
            typeMethod.Invoke(new Selections(), new object[] {});
        }

        [MenuItem("Tools/Gubbins/Selections/Objects with Selected Component", true)]
        private static bool ValidateSelectWithComponent()
        {
            return Selection.objects.Length == 1 && Selection.activeObject is MonoScript;
        }
    }
}