Transmutation

Transmutation is a fun school of magic.  Not the least because it has all the polymorph and other shapechanging magic.  The look on the faces of the enemies when your wizard or other spell caster turns into something completely asskicking is worth the price of admission.  It also has some other useful spells that can buff your allies and hinder your enemies.  But really it's all about the shapechanging.

Art from here
LooneyDM out