If Faith can be knocked out and executed with the perfect Eliza Dushku likeness, I say her.
If not it would go...
1. Willow - Seems to be easier to capture her likeness and with 2 boys to 1 girl, we need another gal to give some balance. No, alternate Buffy does not count as two!
2. Adam - What I said in my aforementioned post.
3. Giles - Every Slayer needs her Watcher, and a 1/4 PF of Giles would look amazing!
4. The Judge - Tremendous character design makes him a great choice to be made into a PF. Downside, he was only on the show for two episodes. Robo Moloch is still the coolest looking Buffy villian (atleast in my opinion), but would be better served as a maquette opposed to a PF because of the lack of cloth material in his design.
5. Cordelia - With her gorgeous face, busty chest, and long legs she would be a fan favorite of many straight male and lesbian Buffy collectors.
6. Xander - My favorite Buffy character in the first few seasons but lost his thunder towards the end. Either way, if they made Xander, we would need an Anya to complete the set. And that's 500 USD of PF madness, which I am not willing to invest into right now. Especially being knee deep in Marvel PFs, and now just getting into Medicom and Hot Toys.
The rest I could careless to get right now.