Tribblix is an operating system derived from OpenSolaris, OpenIndiana, and Illumos, with a retro style and modern components.
NEWS: May 17th 2016: Milestone 17 released, with many updates. This updated release initially available for x86. (Release Notes.)
Update: April 20th 2016: Milestone 16 available for SPARC. (Release Notes.)
While the SPARC version is still pretty experimental, the x86 version is pretty solid. You can download the image, install to a hard drive, and use it.