Inspired by Dawnie...here are my top ten Buffy episodes. Keep in mind however, I've only had 4 1/2 hours of sleep and I didn't want to think too hard. I also made sure to include at least one from each season.
Season 1: Angel
Season 2 : I Only Have Eyes for You
Season 3: The Wish
Season 4: Hush and The Yoko Factor
Season 5: Buffy vs. Dracula
Season 6: Life Serial, Once More with Feeling, Tabula Rasa
Season 7: End of Days
Now I could be subject to change my mind if I thought harder about it, but these are the ones that jumped out at me.