Figured I'd give this a try, I'm not the best at modeling but I'll manage.
Decided on the engineer, because his stock weapons are boring as of now as well as the chance to design a replacement building.
I started up the hat today. I'm going with an aviator's leather helmet. I collected some reference of various types and angles:
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I also started roughing in the mesh, trying to get the basic form and shape down:
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Not to mention the numerous aviator's before this contest. It's a very well done hat already. If you can make yours worthwhile and that much better than the others, go for it, otherwise I'd advise looking for something more original.