Well, let's start a thread on this, but I have a few biggies:
Note - these are commands to be place in your q3config.cfg file in your baseq3 folder and any copies in your mod folders - located in the user/library/application support/quake 3 folder.
From Graeme D's latest .plan:
"Quick update on Mac OS X
If you run with s_chunksize 2048 you get a noticable framerate improvement over the default. Please note that I forgot to latch s_chunksize, so you need to quit the game and restart after you've changed the value of that cvar.
Mac OS X 10.0.4 seems a lot snappier to me too. "
And seta s_doppler "0" (a sound setting, but since we don't have A3D, turn it off)
With these two additions, q3 runs WAY better on X.
Sting