Adafruit Panel Mount 10K potentiometer (Breadboard Friendly) - 10K Linear
This potentiometer is a two-in-one, good in a breadboard or with a panel. It's a fairly standard linear taper 10K ohm potentiometer, with a grippy shaft. It's smooth and easy to turn, but not so loose that it will shift on its own. We like this one because the legs are 0.2" apart with pin-points, so you can plug it into a breadboard or perfboard. Once you're done prototyping, you can drill a hole into your project box and mount the potentiometer that way.