Monsters of Faerun and MM2 are the only ones that regularly get used in games I've played in. Of those, I like MM2 better, for the templates if nothing else. The Rokugan book is excellent, as is Jade Dragons. Monsternomicon is good, but too much space wasted on fairy tales, which I know others really like, but I don't so much. It's also got to much stuff that I'd never use. A few I can handle. It is good, though.