I think that last time I dressed up for Halloween was right before I started cosplaying. Though, cosplay does stand for "costume play", so Reaper-chan does have a point. However, Halloween was originally just a day to worship Satan, and for satanic rituals, before it evolved into a day/night for candy. Really, that's all it's about now for most people; candy.
Ren-fairs could also be considered for cosplay. I have this really neat green and white belly dancer's outfit that I wear whenever I actually go to one. Though, I have kind of grown out of those too. I mainly stick to anime conventions if I can go.