You know what would be nasty? A Dragon Necromancer. And given its other abilities, it could be a Focused Specialist without any real fear of a "blind spot" or weakness in its overall capabilities.
As an alpha predator, it would have access to all kinds of bits it could use for creating animated minions...and if it had the Fell Animate Feat (Libris Mortis), anything it killed with a spell would rise again as a zombie.
Just try to sneak up on the lair of a creature with a small horde of unsleeping, undying, untiring watchmen.