This is a fourteen-sided die with cuboctohedral symmetry. The hexagonal and square faces are exactly the same area, so they are equally likely landing positions. I've verified that it's fair to within 0.5% with 600 rolls of this die.
I'm making it available as a co-creator template so that others can use it as a base for their fourteen-sided die ideas.
There's a 0.1mm hole in one of the square faces to ensure that Shapeways' software sees it as hollow, as described here: http://www.shapeways.com/blog/archives/515-Website-Update-New-Volume-Calculation.html . The hole is too small to be visible in the printed version.