Wouldn't say I use it often, but this thing resolves a domain name to an IP address:

function resolve() {
  case $1 in
    -4)
      getent ahostsv4 $2 | grep STREAM | head -n 1 | cut -d ' ' -f 1
      ;;
    -6)
      getent ahostsv6 $2 | grep STREAM | head -n 1 | cut -d ' ' -f 1
      ;;
    -p)
      getent hosts $2 | head -n 1 | cut -d ' ' -f 1
      ;;
    *)
      getent ahosts $1 | grep STREAM | cut -d ' ' -f 1 | sort -u      
      ;;
  esac
}

All my aliases are just default arguments for programs or shorthands for my other scripts, most of which are specific for my setup.

This is a very good argument for ffmpeg and ffprobe, by the way:

alias ffmpeg="ffmpeg -hide_banner"
alias ffprobe="ffprobe -hide_banner"