7-Zip
Popular open source file archiver with a high compression ratio. Supports packing/unpacking of file-formats like 7z, ZIP, GZIP, BZIP2 and TAR. Unpacks: ARJ, CAB, CHM, CPIO, DEB, DMG, HFS, ISO, LZH, LZMA, MSI, NSIS, RAR, RPM, UDF, WIM, XAR and Z: http://www.7-zip.org/.