BCArchive creates mega-secure encrypted archives
Archives are very easy to snoop into. Heck, Gmail looks into every ZIP archive you get, and won't let it through if it contains any executables. That's fine, and I can see the point of it.
While you can get around GMail's rudimentary checking by simply opting for a different compression format (7z, anyone?), sometimes you want a bit of extra privacy for whatever is inside your archive.
For those cases, BCArchive is just what you need. While it is a proprietary piece of software, it's freeware and it lets you use any of a vast number of established, high-security encryption algorithms. The end product is an encrypted file, either using a password or using a private/public key pair.
The resulting file can also be made executable, which means that while you would have a problem emailing it to someone else, it would be easy for you to decrypt it in the future without needing a copy of BCArchive.
Interestingly enough, I could not find PGP on the list of algorithms the program supports. Perhaps it's there, just under a different name. If there are any crypto-nerds in the audience, please enlighten me – why isn't it there, or what is it called these days if not just PGP?
BCArchive boasts very powerful encryption, but I could not find much information about its compression algorithms. It seems like compression is more of an after-thought on this one, or a way to bundle all of the files into one chunk which could be easily encrypted. Still, when you go for a solution like this, I can see why you would care more about the encryption than the compression.