WinRAR is a lightweight, flexible, and easy-to-use archiving utility that can unpack most archive formats, as well as compress to both RAR and ZIP. Free to try for 40 days ($29 for single license), WinRAR is a top dog in the compression category.
WinRAR's interface is about as simple as it gets. Start creating (or add to) an archive by dragging and dropping your files into the interface or by browsing through the Folder Tree side panel (when enabled). From there, the most common functions are laid out in the form of colorful, mostly intuitive icons along the top, which can all be customized by downloading themes from the company's Web site. You can Add files to, Extract, Test, Delete, or even Repair archives right from the main interface. Drop-down menus house the program's more advanced features, including self-extracting archives, archive locking, benchmarking, and autodeletion of temp files.
With WinRAR, both creating and unpacking archives is blazingly fast. And according to WinRAR's developers, the most recent version of the program takes advantage of multicore processors to achieve even faster compressions rates, depending on your hardware profile. It is worth noting, however, that these speed boosts do use up a significant chunk of RAM (approximately 120 MB). Compression ratios vary depending on file type, but in general seem on par with or better than other archiving programs.
Overall, WinRAR is a winner because of its speed, simple interface, flexibility with file formats, and powerful advanced features. If you're looking for a one-stop archiving shop, look no further.