Love & Monsters
I have the worst taste in women of anyone in the world ever.
Living over the Hellmouth, Xander has had quite an eventful love-life. It's a long running joke that he is a demon-magnet.
Natalie French
In Teacher's Pet, Xander (and most of the male students of his class), fall for the subsitute Biology teacher, Miss French. She invites him over one night for a 'school project' and drugs him. Xander comes round locked up in a cage in the basement, and Miss French shows her real nature: a giant praying mantis who mates with virgins and decapitates them.
Ampata
Ampata was Buffy's beautiful Latino-America exchange student in Inca Mummy Girl. As Xander and her fell for each other, the gang realised that she was in fact a 500-year old mummy, that needed to suck the life out of humans to survive - which kinda puts a strain on their relationship!
Cordelia
Not technically a demon, but well she had her pretty evil moments in high-school! Xander and Cordy have known each other for years and pretty much spend all their time yelling at each other. In What's My Line, they find themselves alone, shut in Buffy's basement and chased by a gross worm-guy demon, and in a moment of insanity... kiss. The start seeing each other in secret, which involves a lot of making-out in cupboards. When their secret is out, Cordelia breaks up with him, fearing for her social status at Sunnydale High, but eventually realises that her relationship is worth more.
Their relationship comes to a screeching halt when Cordy finds Xander kissing another girl.
Willow
Willow and Xander have been friends since they were kids and as they grew older, Willow developped a huge crush on her best friend, but Xander only ever saw her as a friend. Well until Willow went and found herself someone, that is! In Homecoming, as they try on their outfits, they kiss. They shake it off as an accident, but it happens again, and again, and again, and they eventually get caught by Cordelia and Oz.
Faith
Faith leads her life following one simple rule: Want. Take. Have. And that's pretty much what she did with Xander. He helps her escape a tough fight and takes her home. Faith is feeling restless after an unfinished battle and they sleep together. But the next time they are alone, Faith has more deadly intentions.