nemmerle nemmerle nemmerle My ISP is acting wonky so you may have to check this out later.

Let me know if it never starts working.
Ahem, now then...
It's hard to pick a favorite, but the MMII was my first, I bought it used, but in great condition for 5 bucks, got an original Monster Manual the same way, then was given a fiend folio by a guy whose parents wanted him to quit (sucker). The guy barely knew me, but he found out I liked D&D and just forked over his FF and old PHB with the statement that he had to quit anyway. I normally don't have that kind of luck. He lived almost right across the street from my best friend who also plays and knew him better than I. Boy was Dave peeved that he gave me those books.
Anyway, MMII for nostalgia purposes. I also liked the Planescape Monstrous Compendiums a lot, and the Monstrous Manual. Both because of Diterlizzi, and because the PS-MCs had some really cool stuff in them.
Least favorite? I don't know, I don't have any that I really dislike out of the ones I own, the Fiend Folio doesn't have many creatures in it that are usefull to me, but I really like the cool flavor, it's just a weird book! And by the time I got copies of the MM and FF, they were very retro in look, which I thought was neat. So I'll say my least favorite is Monsters of Faerun, just not enough creatures of use to me to make it worth my while. It looks nice, but I wouldn't be getting enough bang for my buck.