7-Zip

There’s lots of good tools for working with archive files, but 7-zip is the best. It can handle almost any archive type: .zip, .7z, .zipx, .rar, .tar.gz, .tar.xz, etc and has great shell integration on windows. It was the first product to use the lzma2 compression algorithm, so it gets stuff a lot smaller than just zipping it (if you use the .7z format).