Definitely! There are many, many useful knots, just the thing for specialized and unusual applications. I like a bowline on a bight with asymmetrical loops for multi-point anchors or hoisting 1000 pound mammoth skulls out of a pit (real case!). But this is not something i do every day.

I am thinking of knots one knows cold, and can tie in very demanding conditions, when speed is of the essence, and one can't tolerate mistakes or booboos.....

If one has three versatile knots down cold, then definitely expand the repertoire. The sky is the limit, once one has a good foundation.