I voted animal lord for PC, since it'd just be fun to be able to polymorph into your chosen creature at will, and have a bunch of them as your allies. It'd also make a nice villain, with say a wolflord (though an Elephant lord would be cool!).
But for villainous nastiness, I have to go with the undead druid prestige class. What was it called again? Just the thought of a druid accompanied by a small army of emaciated, rotting forest creatures is revolting enough to make a great encounter. Or, ooh, what about one of these druids, living in a half-sunken pirateship, with a skeletal crew haunting it, and this druid guarding its treasure with her undead shark minions.