What monospace font is most legible at the smallest size?
My choice would generally be Lucida Grande or Anadale Mono; Some days I'm more in the mood for Monaco though too. If my eyes start getting tired I ditch the small fonts for a few days if possivle. Depending on the shell I'm running, I've had Anadale Mono cranked all the way down to 5 point and still readable (provided I have access to an electron microscope as backup).