Battlestar Galactica - Season 1: Episode 7: Six Degrees of Separation: Wow! One of the best episodes to date. I loved that scene in CIC: Gaius' flippant comment about Number Six as Godfrey's button, his "Where is she?" looking around her. :-) Great stuff!
His descent into madness could be done so poorly, has rarely been done well; it's refreshing to see this cutting between sane scenes, only to realize in the grand scheme he often loses his frame of reference, and that's all some peers need to label madness. Mix that with his guilt... Oh, it's a horrid, delicious brew.
Finally, gotta mention Donnelly Rhodes again. His first appearance was great, and his second didn't disappoint. In fact, only the intimate scene on Caprica between Boomer and Helo disappointed. Red light visible through her skin? Come on! There's your Cylon detector. *sigh*