As people, we often become emotionally attached to the things we love. The mirror in the bathroom, the chandelier in the foyer, the washer and dryer you just purchased after months of saving up. Then when you go on the market to sell your home the inevitable happens and the buyer asks for the item in their offer.
One way to handle this problem is to write in the remarks section of the MLS that the item does not convey, but here's your fair warning, that won't be enough. If you really want to hold onto that important item you're going to need to remove it before placing the home on the market for sale. Otherwise, you can rest assured the buyer will want it as part of the deal.