Horned Chaos Space Marine Helmet
Here are a few fully-scaled Papercraft files I designed quite a while ago. They were sitting on my drive, and I'm still quite happy with them, so I thought I aught to let others take advantage of them. The model colours are optional, and can be disabled in the Pepakura menu.
The files are in .pdo format, which is opened with Pepakura Designer/Viewer. I created the 3D models in Blender and ported them over to Pepakura Designer, and unfolded them.
If you do end up actually making any of these, I'd genuinely like to see pictures!