A custom zsh "widget" for inserting a duplicate of the last argument on the line. Good for renaming a file to a similar name.

.zshrc

# Press Alt-/ to insert the last argument from the same line
# ex:
#   type "cp foo", press Alt-/, and it will insert " foo" so that your command will be
#   cp foo foo
# Great when you want to rename a file to a similar name at the same path
# (This is different from Alt-. to insert the last arg from the previous command)
insertPreviousArg() {
  echo $LBUFFER | read -A args
  LAST_CHAR="${${:-$LBUFFER}[-1]}"
  LAST_ARG="${args[$#args]}"
  BEFORE_LAST_ARG="${args[$#args - 1]}"

  if [[ $LAST_CHAR == " " ]]; then
    LBUFFER="$LBUFFER$BEFORE_LAST_ARG"
  else
    LBUFFER="$LBUFFER $LAST_ARG"
  fi
}
zle -N insertPreviousArg
bindkey '^[/' insertPreviousArg

You can use copy-prev-shell-word (split on shell args) or copy-prev-word (split on blanks), which is built-in:

bindkey "^[/" copy-prev-shell-word

Oh awesome, thanks! I went searching for that before I hacked this together and I guess I just wasn't using the right terms.