Selection.transforms  

// C# example
// Select Objects and make them look to the main Camera by pressing 'l'
using UnityEngine;
using UnityEditor;

public class LookAtMainCamera : ScriptableObject {
[MenuItem ("Example/Selection looks at Main Camera _l")]
static void Look() {
Camera camera = Camera.main;

if (camera) {
foreach (Transform transform in Selection.transforms) {
Undo.RegisterUndo(transform, transform.name + " Looks at Main Camera" );
transform.LookAt(camera.transform);
}
}
}
//The menu item will be disabled if nothing, is selected.
[MenuItem ("Example/Selection looks at Main Camera _l", true)]
static bool ValidateSelection () {
return Selection.transforms.Length != 0;
}
}