N is for Nikki Wood
Nikki Wood was the Vampire Slayer in the 1970's. She became the Slayer when she was 15 and living in New York. Nikki is notable for being one of the longest-serving Slayers (7 years) and for having a child (Robin). Nikki was killed by Spike in 1977 following a fight on a train. Spike then took Nikki's leather jacket as a trophy (which became part of his trademark outfit).
Nikki's son Robin moved to Sunnydale in 2003 (season 7) to be Principal of the newly re-opened high school. He fought alongside Buffy in the series finale and rode into the sunset on that big yellow bus.
Nikki gave us a deeper insight into the history of the Slayer line, and into the lives of these Slayers. Nikki was our proof that other Slayers had been real people, and had real lives, including having a child. Nikki was Buffy's proof that there could be more to a Slayer's life than killing vampires. And she had really cool hair.
After a comment by my mother, I feel the need to explain about the series finale. If you don't want to know - stop reading here.
The Big Bad for season 7 was The First Evil, the source of all evil on Earth. The First Evil first appeared in season 3 as the force that brought Angel back from a hell dimension. The First Evil's plan for season 7 (with the help of Nathan Fillion) was to open the hellmouth and release pure vampires and demons to destroy Earth. They are also trying to wipe out the line of Slayers by killing all potential Slayers - all the girls with the potential to become the next Slayer on the death of Buffy or Faith. The final battle takes place in the High School and ends when Spike (with the help of a magic necklace/amulet) blows up the hellmouth, causing Sunnydale to sink into a giant crater. It's okay though - the Scoobies had arranged for the town to be evacuated earlier on. In order to escape the giant sinkhole, the Scoobies and Potential Slayers (those that were still alive) jumped onto a yellow school bus and drove hell-for-leather out of town, ahead of the sinking town. They stop to admire their handwork, and then drive off into the sunset.
Mum was worried that everyone in town had fallen into the sinkhole with the town.