In some songs, there is a short and accented note at the very end, usually as the last note. Is there a special term for this note besides calling it the "last note"?
In musical theater this is often called a "button" (particularly if it's a low note).
Within the context of a march, this final pitch/chord is often called a stinger; it's used to punctuate the end of the entire piece.
According to this Wikipedia entry:
The last measure of the march sometimes contains a stinger, a I chord played in unison on the upbeat after a quarter rest. Most, but not all, marches carry a stinger. "Semper Fidelis" is a famous march that does not have an ending stinger when not recapitulated back to the beginning of the march. . . . Most marches end at forte volume (loud); one that does not is Sousa's "Manhattan Beach", which ends fading away.
I'm no expert on show tunes, but I would imagine we use the same term no matter what the genre. At the very least, people will know what you mean if you use "stinger" in this context.
A chord at the end of a march that is used to punctuate the ending of the composition. The stinger is typically played by the entire ensemble on the last beat of the last measure of the composition and contains an accent.
A more general classical term for this is a Cadence. Although not all cadences are at the end of the piece, and a cadence need not be a short accented note, though they often are. The sense of finality or closure is definitely implied in this definition though. Sometimes it just closes a phrase and not the whole piece, but there is always some sort of closure.