The Unarchiver is a true example of a perfectly-designed Mac application. Its incredibly simple and easy to use, with the same level of quality and polish as an Apple-made app*, its remarkably flexible when it comes to the filetypes it supports, and if being free doesnt top it all off beautifully, it even has some beautiful icons that help make the app feel right at home on Mac OS X. Overall, even if you dont find yourself extracting uncommon archive formats frequently, just having the Unarchiver around when the need arises is incredibly helpful, and makes the process absolutely painless. *and in fact, The Unarchiver works in the same way Apples standard unzipping app does by default, simply decompressing an archive and leaving behind only its contents.