My sister recruited me with (by pure random accident - she found some eps on a video tape) Beauty & The Beasts and The Zeppo. Not the best eps (although I do love The Zeppo), but they did the trick.

I'd definitely go for a few good standalones. I really liked Earshot, Hush and maybe Fool For Love, as a great look back at the whole slayers-though-history thing. Gah, it's hard to pick just three.