Recs.
Updated
Supported formats:
Packing / unpacking: 7z, XZ, BZIP2, GZIP, TAR, ZIP and WIM
Unpacking only: AR, ARJ, CAB, CHM, CPIO, CramFS, DMG, EXT, FAT, GPT, HFS, IHEX, ISO, LZH, LZMA, MBR, MSI, NSIS, NTFS, QCOW2, RAR, RPM, SquashFS, UDF, UEFI, VDI, VHD, VMDK, WIM, XAR and Z.
SpecsUpdate
Pros
Pro Free and open source
7-Zip is licensed under GNU LGPL, and the *.7z format has support across all major operating systems. There should be no trouble opening the archives under any operating system, and no need to deal with messages bugging you to register or pay for the app. Source code can be found here.
Cons
Con Weird syntax
The syntax of the non-gui versions is different to any other major compression programs.
Con Does not support data recovery
It's not possible with 7-zip to add data recovery records to the archive which could repair minor integrity errors.