Have you ever watched an unfortunately-timed ad after a certain key scene on a television show?
This Battlestar Galactica clip has just that. It's a 3+ minute clip, but the ending is so totally worth it. One of the most creepy things I've ever seen, like something out of the mind of Kubrick (or early Peter Jackson). I almost vomited, so you know this is choice.
SPOILERS in the clip, so if you don't want to be spoiled for BSG, don't watch. Also, sort of NSFW.