What are some of your favorite and creative ways to use spells? One of my favorites is to cast a Frost Atronach in a doorway or passageway so that enemies can't get around him. Then I cast some Ice Storms which pass through the atronach without hurting him, but killing all the enemies.
All spell tactics are welcome including ones which use spells from the DLCs and even Vampire Lord ones since those are magic too.