Felon said:The biggest problem for me is that monster classes aren't OGL, and support from WotC has been spotty at best.
The version in SS, no, but some third party publishers have come up with similar material that is open content. Maze of the Minotaur from Behemoth3 and Shaping the Self from Genjitsu come to mind.
As for a creature I would enjoy playing:
From Minions, the vapor bore has some possibilities for a high level campaign. For a very unusual campaign, the hearth horror would be interesting to play (with the other PCs as allied evil creatures).
From the SRD, aranea, ettercap, troll, aboleth, barghest, behir, chuul, couatl, gargoyle, manticore, water naga, and rust monster (popular with the druid players).
I really don't want to dig up the other books so I will finish in the morning.