Hey sweetie, if you're still looking, I'd love to do any of these!

Demon x Human*
Angel x Human
Vampire x human
Assassin x Client
Assassin x victim
Ghost x human
Undead x living
Witch x Warlock
Pop star x fan
Bad boy x good girl*
good boy x bad girl*
Slave x master*

If we were to change pop star x fan to just a rock star or something, I'd be very interested. Otherwise, slave x master is always fun!