What an awesome thread! :-D
I had to go for Mordor Orc, as it was quite challenging to design one, first of all cause the variety of Mordor Orcs in the movies is quite big, they don't have an official uniform and it was quite hard to pick one, base design on it and make it as a generic character. I made many versions of it and in the end I ended up merging few and keeping it simple! ;-) This character was also a "last minute" decision so I was quite happy that I managed to throw it in!:-)
There's also a new video uploaded on the LEGO web telling a bit about design process when making minifigures, go and check it out ;-)
http://thelordoftherings.lego.com/en-us/Videos/Default.aspx
Regards!