The Unzipper extracts .zip and .rar archives or .gz files on webservers. It detects .zip/.rar/.gz archives and let you choose which one to extract (if there are multiple archives available).
It's handy if you do not have shell access. E.g. if you want to upload a lot of files (php framework or image collection) as archive - because it is much faster than uploading each file by itself.