I'm sure many of us are familiar with this one-shot Vader helmet from the ILM book:
There is a little info about the helmet over at Jez's site (I borrowed the pic, which is a scan from the ILM book, from there thanks Jez!). The helmet/costume apparently were a one-off and rumor is that it met its end at a rather rambunctious party (there appears to be some possible damage in the pic above--notice the left side of the dome).
I had always assumed that Joe Johnston made the helmet but that assumption is based merely on the fact that he's the one wearing it in this pic (well, that and his involvement in making the Fett helmet).
I'd love to know more about this particular "concept" helmet as it's the only one we know of that was actually produced within the Lucasfilm sphere even if it was just for kicks.
Paging Mr Bies...