Draconomicon (3.5) was great! So was the Eberron Campaign Setting, one of my favorite books.
Ahh, the ol', "It's only broken if you use it the legal-yet-arbitrarily-wrong way," argument!Yay for rules loopholes that make no sense in context. It was a power innate to a rare to the point of being nearly extinct and virtually unknown race, that could in theory be combined with things from other books that were never intended to be used in that way, etc etc.
Don't blame Serpent Kings for Char Op notions taken to absurd levels.