7-Zip

While the ZIP format has been the most commonly used compression format for decades, there are many different formats out there, especially on non-Windows operating systems. This is what makes 7-Zip such a powerful and useful tool. It can unpack just about any compression format, and it can create many different types of archives as well. Among the formats it can both read and write are its own 7z format and ZIP, Gzip, bzip2, tar, WIM and xz. It can also unpack the following formats: APM, ARJ, CHM, cpio, DEB, FLV, JAR, LHA, LZH, LZMA, MSLZ, Office Open XML, onepkg, RAR, RPM, smzip, SWF, XAR and Z archives. It can further read disk images, too, such as CramFS, DMG, FAT, HFS, ISO, MBR, NTFS, SquashFS, UDF and VHD. Among its many other useful features is its ability to create both self-extracting archives and password-protected archives. It further uses a 256-bit AES cipher and can take advantage of multi-core processors. Best of all, it is completely free to use. The only real negative aspect to using the software is that creating archives with it can be slow and resource intensive, especially in comparison to other similar utilities. There have also been some security vulnerabilities in the past relating to the software.