5. 'Graduation Day' (Season 3, Episodes 21-22)
A blessedly straightforward season finale full of pure Buffy fun. The double episode has the Scoobies battling to stop the catastrophic ascension of Mayor Wilkins, the sorcerer mayor of Sunnydale. On the way we get an epic fight scene between Buffy and slayer-gone-bad Faith, the politician's transformation into a giant snake demon (any resemblance to folks currently in power is, of course, completely coincidental) at the class of '99 graduation ceremony, the death of Buffy's longtime nemesis Principal Snyder, and, naturally, the destruction of Sunnydale High in a massive explosion. The season literally goes out with a bang.