Used to use it as a benchmark back in my Pentium 2 days. It basically fly's around a 3d city with a matrix theme, and reports FPS as it goes. It's called "Matrix III".

Voodoo files had it but it's no longer there. If anyone has it, I'd love to have a copy for old times sake. Here's the link of what it was on voodoo files. There's a screenshot there, http://www.voodoofiles.com/3376