Hmmm...I was King Tut one year (back in the 70s, when he was fashionable); my mom made the Eygptian costume based on pictures from the bible.+LOL+
I was a robot one year, too. That was cool, but I couldn't see....kept running into things.
We always go to a friend's costume party the weekend before Halloween. Two years ago, I was Homer Simpson. I wore a big Homer mask, white collared t-shirt, nerdy old man jeans and brown shoes. I also covered my arms with yellow greasepaint (it kept smearing and getting on everything. I also had a can of "Duff Beer" (a container for a deck of Simpsons-themed playing cards). Won first prize that year! WhoooHooo!
This year, I'm gonna be Darth Vader "HOOOOOPHoooooooHOOOOOOPHooooooo.............." (Vader breath).
My wife is going probably going to be Princess Leia. The party-throwers usually try to do a "couples" theme; one year we were Sandy and Danny from "Grease", another we were Bugs Bunny and Elmer Fudd...you get the picture.
I bought one of the whole-head voice changer masks (they said it should fit me okay) and a light saber from Wal-Mart (post-Halloween, they'll make a cool addition to my collection). I'm also going to bring a boom box with me so's I can make a cool entrance to the "Imperial March". "Dum-Dah-Dum-Da-Da-Dum-Da-Da-Dum....."