PK3 - Quake 3 Engine Game Data File is a file extension for compressed game data files that are commonly used by the Quake III engine. This extension will give you many different choices for maps, textures, audio clips, and many more. All of these features are great to have because they can all be used when it comes to playing your games. These types of files are very similar to .PAK game data files as well. They are a much newer format though. You will need to make sure that you save the file in a known directory so you can access it when you want to play related games. Arena, Star Wars, and Solider of Fortune II are just a few games that are supported through this file extension. If you want an extension that is full of different features, this is the route that you should take.