Given that I spend most of my working time on a code editor (including to write papers), I regard the choice of the font as quite important. To me, a programming font must be monospaced (programming without a monospaced font is quite challenging) and appeal to me (a matter of readability and aesthetic I guess).
There are tons of fonts nowadays and it is quite easy to create your own (see for instance fontstruc), so the choice is wide! Some people that propose selection of programming fonts, for instance on hivelogic.com, very helpful.
Currently, I am using mainly two sets of fonts: the ones by powerline and the FiraCode fonts. I set up Atom and my Terminals with Ubuntu Mono derivative Powerline and Roboto Mono for Powerline and I am experimenting FiraCode fonts in RStudio (see below). I was not aware of programming ligature before using FiraCode, it’s really neat.