I chose Xander. My second fave would have to be Giles.
Xander means well! He's just the normal guy. He always tried to do what was best. He wasn't blessed by having superstrength or magical powers. He isn't The Key, or a Chosen One, or a vampire or demon. He isn't phenomenally brilliant. But he loves. He's a friend. He does his best. He's the most real character on the show and it was this real character that saved the world. Because in the end, it doesn't matter how much magic you possess, how many baddies you've slayed, the love you have in your heart counts. And that's exactly what Xander exemplifies.