Barghests - What, no barghest love? Listen berk, it's a must.
Mohrg - I always loved these guys. They're really messed up. Odd kinds of undead are always good to stick to players. I thought these were inspired.
dinosaur (velociraptor/deinonychus)
Linnorms or sea serpents.
31. Frost Worm (12)
This. I would love an "Exploration Manual".
Yeah, 2E Council of Wyrms setting. But there was indeed a 3E set of dragons as 'monster classes' for PCs - in Dragon Magazine. (Issue 320 had the metallics, Issue 332 had the chromatics.)I don't know about WotC, but TSR produced a rules option for playing dragons as PCs. It's actually the original source of half-dragons as PCs, too, if memory serves.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.