I installed z which is great. Then I started thinking about all the available one letter commands in bash/zsh. So I went through them. This is the result.
$d lists recent dirs
$g a git shortcut
$l shorthand for ls -l
$t It's just after a quarter past twelve.
$w Show who is logged on and what they are doing.
$x X - a portable, network-transparent window system
$z zsh fast finder