How to single label a point in pgfplots with text?

You can set the contents of the nodes by using the optional argument to node near coords=<content>. By default, it's set to \pgfmathprintnumber{\pgfplotspointmeta}, but you can use any text or code. To use the static text mylabel, you'd say nodes near coords=mylabel:

\addplot [black, mark = *, nodes near coords=mylabel,every node near coord/.style={anchor=180}] coordinates {( 0, -1)};