Spectral Cornell Box
This Cornell Box was rendered spectrally, using actual light wavelengths instead of binning everything in RGB channels. Note there was little point in rendering this spectrally, since the dependence on wavelength was not very complex, but it was a test. Notable advantages of spectral rendering include dispersion (i.e. rainbow effects with prisms which cannot be done the "standard" way) and fluorescence, where an object changes color depending on the color of the light illuminating it.
The light was a sphere poking out of the ceiling, following a black-body emission spectrum with a temperature of 3500K.