20 minutes, OpenSCAD, a crying baby and a triple espresso yield something that from the appropriate distance (say, perhaps low earth orbit) looks slightly like Guy Manuel's helmet.

More or less done to prove the point that basic OpenSCAD is dead simple. This model is made of ~20 cubes, 5 spheres and 8 or so cylinders.

TMR posited it might take half an hour to make a d20 in Sketchup... it took 35-40 minutes, including figuring out a good process.

For the record, I used TopMod to generate the original twenty-face regular solid (it's an icosahedron, I believe, but my memory may be faulty), and I also cleaned up in Meshlab (couple clicks just to make sure the mesh was ok).

It Skeined great, at least for the jumbo size dice.