Well, let's see... I'm a guy so Slayer and Witch are out. Magic is dangerous and corrupts so I'll avoid the Warlock category. Werewolf, too much shaving involved and too few benefits when you're actually in control of yourself. Assorted demon types,,, maybe I'm just old fashioned but I kind of think the whole 'no soul' thing would be a bit of a turn off. Regular joe human type? Nah, in Sunnydale they generally end up dead or as vampires anyway.
I'll go with 'Other'. Think I'll chose 'Slayer's love interest'. Now that would be an enviable position. Sure, you could say that's essentially just a run of the mill human with no powers and a butch girlfriend. However, if you were to do so, I'd simply ask the Slayer really nicely to hand you your own backide and watch with glee as a five foot nothing size 3 beats the heck out of you.