Considering all of the pirate themed things that happened this year, I think many people are going to be dressing up as a pirate. My idea to differentiate myself would be to go as a software pirate. (Requires a couple of books on 6502 assembly language programming, and talking about my upload download ratio).
Another idea is go as a microbiologist. That's pretty easy, as I'd just need to borrow timer from work and wear latex gloves, as well as disappearing for a bit to go "feed my cells".
The idea that's currently winning is to go as a femme, though for that idea I'd need to go pick up some makeup.
The last idea which I doubt I have the time for, is to go as a tolkien elf.