I haven't really thought about it, to be honest. It's a little early for me and I'm not quite sure if I want to do dress up 'cause I think I'm a little too old. But I suppose it'd be appropriate since I'll be passing out candy.
I suppose if I had to choose right now I'd go as the vocaloid Megurine Luka o Hoshina Utau from Shugo Chara. I'm leaning twards Luka because she'd be a bit easier because Utau has some pretty wild pigtails...