Bach, difficult to discard any of his pieces!!

But if I think Bach, the first that comes to my mind are the Goldberg Variations, in performance of Glenn Gould

Then, Chaconne, which is actually a movement from a Suit for violin, but there is an arrangement for piano, by Busoni.

But, The French suites can also come, if I come to France to this piano-lunch-siesta event :))
This one is beautiful