The Unarchiver
From the get-go, it's obvious what The Unarchiver does. It can easily unzip or unpack any files that you want. Even though the program might have an unimaginative name, it gets the job done without much trouble and complaint.
The program was developed by Dag Agren and available for free download on the Mac App Store. It works great on Mac but it's also possible to run it on Windows or Linux. You just have to follow a few things before you can get it up and running.
It's a nifty little tool that's easy to navigate and understand. Best of all, you can easily open any file you have since it supports a great selection of formats. Give it a try.