Software I use (and recommend)

vim
my main text editor for about 2 years now
dwm
the wm I use. It can be pain to setup, but otherwise works as it should.
dmenu
simple, but works as it should
feh
simple and fast image viewer, probably included with your distribution.
VLC
I’ve never used any other music player
mutt
terminal email client
tcc
just another incredible thing made by Fabrice Bellard

And software you probably already know like awk, ssh, rsync, R, latex, and git.