My vote goes to NeclordX's genderbend of some really famous Japanese warrior that I don't recognize because I don't know shit about Japanese history. All I know is that it's one of the most daring and innovative reinventions of the samurai trope I've ever seen on the forums.
I was initially turned off by the over-saturated colors, but the more I paid attention, the more the design grew on me. The first thing you notice is that the helmet is cleverly executed, distinctly Japanese, and, most importantly, super dramatic. Next, color balance is masterfully executed. Every color is echoed somewhere throughout the body, yet the colors are spaced apart enough to still maintain a rhythm (i.e. avoids the jumpsuit syndrome). Emphasis is achieved with the red crescent, scarf, and weapon. Finally, the proportions are excellent. Some creators use pieces of equipment with little regard to item bulkiness or their creations' overall silhouettes, but this lady samurai is streamlined from head to toe. I'd only make two changes: lower the saturation and eliminate the pattern on the shin guards, maybe add some bump-mapping. But all in all, bravissimo.
Notable contenders:
1. Koko's Oichi and Orange's ladies are visually stunning, well researched, and well executed, but this challenge's focus was really supposed to be on the warriors, i.e. people trained and dressed to kill.
2. Orange's Takenaka's got a kickass helmet but a comparatively plain outfit and a really, really distracting shoulder wrap. This creation has a lot of potential though. I'd love to see a revision.
3. Meanbeard's Takenaka's got masterful execution, but it's realistic to a fault. He does have a fur motif and a nifty mustache, but other than that, it's an old man in a blue-grey uniform.