I would use it to render huge fractal images, do interesting and complicated path tracing (ie physically-based raytracing in mantra or luxrender), and explore r

I would use it to render huge fractal images, do interesting and complicated path tracing (ie physically-based raytracing in mantra or luxrender), and explore reaction-diffuson simulations. All assuming, of course, that completeley parallel and compatible code is available for all of these. Edit: happy to write such code myself too.