So, ehm, a little discussion took place between me and Muerte in Steam, and we couldn't come to a conclusion.
My point: "sans-serif", "serif" and "monospace" aliases must be included in the list:

Because simply selecting, for example, Courier New to highlight a variable will not make it highlighted on some linux systems (Ubuntu, for example, doesn't include Courier New).
Selecting "monospace", on the other hand, will make it so the end-user browser will choose between "Courier New" and "Lucida Console" by itself. So the variable will stay highlighted even if you browse from toaster.
Muerte's point: he better explain it himself. But things I understood from him:
1. Monospace isn't a font, it's a font family, so including it in the same list will confuse the users
2.
it is better practise to really define the font rather then let the browser decide for you
so you have control over what happens
3.
and people can customize however much they want anyway by typing it manually
Update: In the end of discussion Muerte agreed to make group titles (
Serif, for example) clickable so that they will insert the proper font family.
What do you guys think?