The main watcher on Buffy The Vampire Slayer. He was the watcher in Season 1, 2 and most of 3, until the council "fired" him. He still hangs around though. Played by Anthony Head.

A vital fact that most American watchers of Buffy will have missed is that "Giles" had a previous existence as one of the most well known characters on British TV as the Gold Blend man, a principal character in an interminable series of "romantic" instant coffee ads somewhere back in the big shoulder pads era. Which did get granted a token in-joke ("God, this coffee's disgusting") somewhere near the beginning of the Buffy-goes-to-college series, which is currently running on the BBC, no doubt a year or two behind the USA.

(update a year or so on): Anthony Stewart Head currently has a role in the BBC's comedy series "Manchild" playing a 50-year-old divorcee with an eye for much younger women (but suffering from a few technical problems). He still comes over as if he's playing Giles, though maybe it's just the accent.

1.) The character seperation neccessary for Buffy and the Scoobys to become real adults, with no adult supervision (because, err..they're not kids anymore....but that means I'm not either, which is scary...anyway..).
and
2.) The fact that Anthony Stewart Head is going to get his own show on ye olde BBC, still in the character of Giles. The show hasn't gotten kickstarted just yet, according to the BBC's site, but you can find out some info here:
http://www.bbc.co.uk/cult/buffy/news/01061902.shtml

Apparently, Joss's ambition is to do an "adult" show, a Scooby gang for adults. There are already plans to premiere it on BBC-America at the same time as in the UK, so us Yank fans of Mr. Head will get their fix too.