Buffy
Xander
Willow
Giles
Cordy (as both foil and semi-scooby, up to s2 Angel)
Joyce (who has a surprising amount of good moments, from snarking at Snyder to hitting Spike with an ax, and even counseling Spike)
Snyder (love to hate)
Mayor (I think a case could be made that he's not as bad as many real world politicians)
Illyria (fascinating, and really shows off the actress's incredible skill)
Wes (s3 Angel on, though the love triangle nonsense nearly knocks him off this list, but that weighs down some other characters even at the top of the list as well). He has "fierce competition" from both Jenny and Faith for my final slot.
(Dis?)Honorable mention: Spike, but only season 2. Had he been killed off this season (at least not returned in Buffy's show) as originally planned then he'd actually be on the list for Top 10 favorite.
And gotta say that the Angelus arc in season 2 is what made Buffy a favorite of mine, creating something of an obsession (in case it's not obvious I DON'T ship Angelus with anyone)