Linux or BSD? both, happiest with arch and openbsd

Vim or Emacs? vim, tho i keep looking at vile, and use ed on servers

Systemd or init? init, maybe in 5 or 10 years systemd will be mature enough -- are logs in /var/log or journalctl, which target is the recovery/omg-its-all-borked target, '\S+ is taking a long time'...

Languages? C, perl, python, ocaml, golang -- nowadays mostly just python and golang for work, with ocaml for project euler.

Why unix? ease of automation (free tools!) and stability of interface (when was the last big backwards incompatibility in vi or emacs or TeX?). its bias against unnecessary change is a huge advantage in a world that already has more necessary change than we can process.