My thoughts on who is a Cylon:
Starbuck - there seems to be a possibility thanks to this whole Eye of Jupiter painting that she indeed "has a destiny". Whether that means she's a Cylon or not though remains to be seen. Whether she's a good Cylon or a bad Cylon though, the fact remains that Cylons are machines, created by man, and Starbuck just seems, well, too
human for that to be the case with her. I think she can have a destiny and so forth without being a Cylon - after all, Rosalyn had visions, etc. and is not a Cylon - or is she...

Seriously, since she had cancer and was cured by Cylon blood, I don't see how she could be - same with the Adamas, being that Bill had kids, etc. etc.
Baltar - almost too obvious now, so doubtful in my mind. It would really come down to what makes the final five models "special", and if that would then add a totally new element to Baltar. It's almost as if he
wants to be a Cylon now, as if that might provide him with some type of twisted redemption, so I think in a way it might be further torture for him to find out at that at the end of the day, he's just a normal human.
Now for the fun ones...
Saul Tigh - I think it would be funny to have someone who loathes the Cylons so much to find out he is one. What be be even funnier would be for him to then kill himself as a result and then resurrect somewhere, realizing he can't die. His own personal hell!
Chief Tyrol - The two reasons I think it would be amusing for him to be a Cylon would be because he's had a child ("See, having a hybrid isn't that tough!"

) and more significantly, it would add so much beautiful irony to the initial speech he had with Cavil when Cavil said, "You're not a Cylon because I'm a Cylon and I don't recognize you from any of the meetings". "Yeah, it's because I'm one of the other five, so

"
Helo - This would be hilarious because it would then mean that Hera is not a hybrid after all and is simply the product of two Cylons.
Yeah, just felt like having some fun with those ones...
