Built entirely out of cardboard, clothes from GoodWill, and some bits of Velcro. It took me about two weeks of construction, and my apartment was an absolutely cluttered mess the entire time. The head was definitely the hardest part, since General Grievous's head is much narrower than mine and only half as large vertically, but it still had to fit. The chest was the next hardest part. My first attempt was so form-fitting that I couldn't get it off, and ended up having to rip it open. Just about every other piece had its own snags, and there's a distinct drop in quality with the legs as I was running out of time. I wasn't even able to finish the feet and had to just wear black shoes instead. Still, I think it turned out pretty awesome.
It was a big hit at the party, but it was a bit difficult to eat and mill around while wearing it. Also, and you may be able to see from the above picture, I had to be continually wary of the Velcro keeping the cape attached from coming undone. (A slightly disappointing aspect of the cape is that you can't see much of the upper arms or shoulder guards.)
Apparently, Grievous is also quite the ladies' man.