Right now it's zsh for interactive use and whatever /bin/sh happens to point to for scripting. Only feature zsh has that I actually use and no other shell has is the rc_quotes options, helps when writing commit messages inline so you can type "it''s" instead of "it'\''s". I actually used rc as a login shell for a little while and it works pretty good except for retarded programs like vim using shell syntax to do shit like redirection (lol) and lacking job control which I don't use much anyway, tmux does the "run multiple programs and switch between them" thing easily and better.