I'm going to replace an existing 3-hole faucet with a single hole faucet in my kitchen sink. I plan on installing a soap dispenser into one of the other holes, but that will still leave me with one empty hole. Aside from faucets what accessories are available that fit into faucet holes?
Another use is an air pressure switch for a garbage disposal/food grinder. When we moved in it took a while to discover that using the garbage disposal required opening the cupboard door and reaching underneath the sink for a switch. When we too went from three fittings to one I got the chance to install an air pressure switch in one of the spare holes. (A soap dispenser went in the other hole.)