What are you guys' favorite singular composition of all time?

I want to know yalls favorite singular composition that functions as a self-contained, relatively short work. Think of a Miniature, a Character Piece, a Lied, a short Prelude, or an intermezzo or a standalone rhapsody.

We are excluding complete multi-movement works like symphonies, sonatas, concertos, operas, oratorios, and also excluding single movements taken out of a larger composition.

Essentially, what is your favorite complete classical piece of music, generally under 15 minutes, that was conceived as a whole, standalone work?