Eliza Dushku but she's queen of cult cancellations.
Michelle whateverberg was the younger sister she was doing pretty well for awhile.
The dude from Bones is probably the most successful of the lot.
Well no Gellar is the most successful having been in number of big movies like Scream 2, Cruel Intentions, The Grudge etc.
Outside of her I would actually say Hannigan.
James Master played Spike and AMH played Giles the Watcher to answer deezy's question.