Oh dear...I shamefully admit I've gone as Vergil at one point, the outfit was bought, the Katan I'd owned for a while and I'd already bleached my hair white.
Nothing creative really, the costume is pretty much easily bought on a site like eBay, the sword was easy for me, considering there WAS a shop near here that sold them, but because of new laws making it illegal for swords to be sold to the public, it may be a lot harder to get one now.