The Willard Nickel or Dime pool cue tip shaper is a simple yet very effective tool that should be in every player's bag. The carbide grit forms the perfect nickel (WSNA - 10.5 mm) or dime (WSDB - 9.1 mm) radius on your cue tip. The proper shape gives you better ball control and the ability to better chalk your cue.
It's compact size allows you to fit it in your bag or your pocket on league night. It also has a hole to allow you to place it on your key ring.