"I'm pretty certain it's Gaeta (Alessandro Juliani), which I just love. And hey, a big plus that he's gay - whoo for Cylon diversity!" - tmsassan

I think it's Starbuck (Katee Sackhoff); One of the clues on Sci Fi's site says, "You have heard my voice countless times, and yet do not know who I am" - dalin345

"Ellen Tigh (Kate Vernon), though presumed dead, could be the final Cylon because of her betrayal of Saul on New Caprica." - foxeee

"Dee (Kandyse McClure). She is the final Cylon. Her secret mission has always been to influence Lee, who is the single most important character to the series when you think about it. - thewilhms

"I've always kinda thought the final Cylon should be Doc Cottle (Donnelly Rhodes)... it opens up all kinds of possibilities!" - newfers

"I'm gonna say Romo Lampkin (Mark Sheppard). He did influence Lee to leave the military to become a barrister, which led to him being an interim president, and more importantly, he influenced him to defend Baltar." - JREngle

Admiral Cain (Michelle Forbes), also presumed dead, was in a position of great power, which would have benefitted the Cylons. She also had an affair with one of the 6s before it was revealed she was a Cylon - jealoustater