Common GUIStyles used for EditorGUI controls. These are set up by calling EditorGUIUtility.LookLikeInspector and EditorGUIUtility.LookLikeControls.
Note: This is an editor class. To use it you have to place your script in Assets/Editor inside your project folder. Editor classes are in the UnityEditor namespace so for C# scripts you need to add "using UnityEditor;" at the beginning of the script.
Use these styles to make GUI that looks native to Unity.