I gotta go with Season 2. We get to see Angelus at his best this season. Throw in Spike and Dru, and you have the makings of a legendary season. There were so many other great things this season as welll. You had The Judge, Those Bounty Hunters after Buffy, Oz the Werewolf, Xander and Cordy together, etc. It was also one of the most tear jerking seasons in my opinoin as well. When Angel lost his soul, when Angelus killed Ms. Calender, and when Buffy sent Angel to a hell dimension. I also loved how Spike went to Buffy in Becoming Part 2 and formed a truce with her. Bloody Brilliant!!!!!