Cool: Galactica FTL jumps into the blue skies above New Caprica, burning as it free-falls through the atmosphere, sticking around just long enough to launch its Vipers before jumping away again. A real showstopper of a visual effect.
Cooler: Tigh unexpectedly puts his money where his mouth is and kills his misguided wife Ellen, punishment for her having helped the Cylons. This guy is becoming a real force of nature. His days of drunken, ineffectual self-loathing seem a thing of the past - his time in the Cylon detention center have honed him to a steely point.
Coolest: The predictable self-sacrifice of the Pegasus, as Apollo defies Adama’s orders and swoops in to save Galactica from certain doom. This sequence, which is capped the empty Pegasus ramming one of the Cylon basestars (which takes out another basestar after the explosion sends big chunks of Pegasus flying everywhere), is one of the most thrilling space battles since The Wrath of Khan.
Huh?: Gaeta gives Baltar a chance to redeem himself by going to stop the Cylon nuke planted on New Caprica. Okay, but by the time Baltar goes looking for it, the planet looks completely deserted. Everyone’s already evac'd to Galactica, so who cares if a nuclear bomb goes off?