In the spirit of the "What Browser..." thread:
What Fonts do you always return to?
Personally I used to be in love with Roboto anything but I recently discovered the Fira (Mozilla's font family) series.
I have it as my default font in everything now, my only problem with it is that it lacks a Serif option, it only has Sans, Coding and Mono.
Needless to say I am running Coding in my terminal. It is the one terminal font I find easily readable at 8pts in the Terminal, btw (tho I usually run my terminals at 12 points font size).