Neil Dickson - Own OS
Own OS was an operating system being written from the ground up to be ideal for High-Performance Computing (HPC) and other dedicated server systems needing low overhead and high CPU performance. It was designed to support up to 15 x86-64 processor cores with SSE3 and up to 512GB of memory (per node), to push the limits of computing power at the time.
Instead of taking a very long time to make an OS that is mediocre at everything, the idea was to make an OS that is very good at one thing and make it easy to modify to be good at other things people want. It didn't quite take off, but it made for an interesting undergraduate honours project.