A really fun and easy thing to dress up as is a drag queen - just find the brightest, funkest dress you can, pair it with a feather boa, and wear as bright, over the top make up as you can, with lots of glitter!
I mainly dress up as rock stars or other figures of pop culture, as they usually require minimal effort and cash to find a "costume" (I just dig around in a thrift store or use my own clothes, sometimes I don't even have a costume until half an hour before I leave for school), and allow me to be "in character" all day, which in really fun.
Last year I was Bono, the year before that I was Deborah Harry, and this year I'm thinking of dressing as Kitten from Breakfast on Pluto, or as a Harajuku cosplayer (despite the fact that I tend to dress up like that randomly, not just on Halloween). Either way, I'll porbably hafta learn how to use my sewing machine.
Last year I was a "Graduate from Hell" but this year Im thinking of maybe being a witch 
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I've got a great tartan/plaid mini-skirt, a lacey low-cut black top w/a shrug & some kick-ass knee high combat boots.... throw in a pair of fishnets & some darker than normal eyeliner, my own mother probably wouldn't recognize me! 
Have to admit though some people in my area for the past couple of years haven't really gotten in the Halloween spirit. Rather disappointing because when I was growing up just about everyone in town made it a big deal. Couldn't imagine going without celebrating.
