I've been slowly working on a 3D file manager that's operated like a first-person shooter. I was originally inspired to think along these lines by DOOM for sysadmins, and other people have tried similar things (Brutal File Manager, Virtuadesk) but nothing I've seen quite matches what I wanted to try. So, I started to develop it.
I'd suggest reading the design document to help understand the screenshots below. Click on the thumbnails for larger images.