There are others out there.
FnQuake3 / Fappin' Quake3 - ioq3-based and comes with a bunch of enhancements including postprocessing, fixed overbrights and widescreen support. Unfortunately it's very obscure to find.
Q3Vogons - based on the original source release to add minor fixes, widescreen expansion support, and paletted texture support for the older 3dfx Voodoo cards.
ChallengeQ3 - should be excluded since it is exclusively designed for the CPMA mod, and it strips features for performance. Listing here for completeness.
Q3MME - A source port designed for demo playback, adds a bunch of shader effects and optimizes the renderer even more. Since it's specialized in the demo function for presentation purposes and not general purpose playing, it should also be excluded.