This is a costume I made for my hubby for Amecon 2008, it's a bit of an obscure one it's the Green Onion Alien from Gantz (reference pics at bottom of post). The hardest part of this costume was the grassy hair, I had to get the right texture wig and then cut and dye it using marker pens, nightmare!! Worked pretty well in the end though.
We had fun getting lunch lol!!
Here's some character reference shots from Gantz. It's one of the most weird, gory and odd anime ever! Worth a watch tho!