It’s not quite the Home Run Apple, but the Keyspan sign has been a component of the outfield vista for a decade. At least it was [1] until the Mets began their latest homestand with a vertical National Grid banner taking its very tall place. Sponsors come and go, signs change frequently, but I had gotten kind of used to no Met ever hitting the Keyspan sign. There will barely be time to get adjusted to no Met ever hitting the National Grid sign.
Keyspan has changed its name to National Grid, but Keyspan Park [2], as far as can be presently divined, still exists as named.
Citi Field, of course, will always be known as Citi Field.