What song does Elton John repeatedly deny requests to perform?

As Elton John winds down what by all accounts is one of the all-time greatest careers of any musician to have ever lived, it's fair to wonder if he'll play one particular song live ever again.

Currently embarking on what he's called his final tour (or by the time you're reading this, perhaps it's already over), Elton John is known as a crowd pleaser. It's not often that you wouldn't hear the majority of his most popular songs at a show.

So which song does he consistently deny requests to play?