I was thinking about Arcs on Buffy, mainly character arcs. Like, Buffy's arc goes beyond the show, that's why she never says anything at the end of Chosen. But Giles' arc goes on during the show, the entire series. Willow, has multiple Arcs, her big one, toward the end of the series(the magic addiction, and the being gay one).
Xander though, he doesn't really have an arc. Sure, he has episodes about him, and he had the small-ish 'Anya' arc, but if you look at it, he's more of the one who supports them all. Some people mistake that for an unnecessary character, but Xander isn't unnecessary, he's the backbone. He's saved so many lives, more than Buffy, because he saved Buffy. ('Prophecy Girl')
Xander is my favorite scooby and I love him soooooooo much. I don't think the world could exist without Xander, and Xander-type people.