Works Great for RAR Files
I got this specifically for .RAR files, and it works perfectly. It was easy to use and very fast. While most file compression formats are supported natively, at the command-line if nothing else, .RAR seems to be an exception.
Several people have complained about issues opening .ZIP files with it. I would suggest that perhaps the .ZIP files involved are corrupted or otherwise compromised. OS X opens them natively and transparently, so there would be no reason to use this program or any other 3rd party program for them.
wolf.nbm about RAR Extractor - Unarchiver