Someone went and made a Companion Cube computer case from Portal. It looks good and is small (20cm). It's used as a web browsing and music computer, so there isn't anything too fancy on the inside. Unlike the doughnuts I had for breakfast, which were chock full of fanciness. And by fanciness I mean Bavarian cream.
A few more pictures and a link to the build through the portal.
The Weighted Companion PC [bittech]
Thanks to Bre, who would make a faithful companion but not a cube, for the tip