2. 'Hardhome' (Season 5, Episode 8)
Bran Stark's plunge, Ned Stark's death, the Red Viper's skull-crushing, Jon Snow's assassination – all of them take a back seat to this episode when it comes to shocking the entire Game of Thrones audience. With no precedent in George R.R. Martin's novels, which merely allude to a cataclysm at the titular village without giving us a clue what happened, "Hardhome" stunned book-readers and TV-viewers alike. After an ominous buildup, the armies of the dead descended on Night's Watch and wildling forces alike in a literal avalanche of walking corpses, guided by the demonic Night King. As Jon Snow sailed away from a legion of zombified humans, the true menace of the White Walkers was made unbearably clear.