When all you've got is a hammer, every problem looks suspiciously like a nail. RarZilla is a great little utility for automatically "unraring" RAR archives, but it's incompatible with any other archive format. Depending on what you're looking for, the program--which is also available in a portable version--is either just the tool you need or woefully inadequate.
The program does a wonderful job of unzipping--sorry, unraring--RARs, and it provides three methods for achieving that lofty goal. You can select the "RarZilla!" option from the context menu associated with any RAR file in Windows Explorer, you can double-click the RAR, or you can drag and drop the RAR onto the program interface. To aid in the last one, the program is permanently set to live on top unless you minimize it. I found that extremely annoying, but your mileage may vary. It extracts the compressed files to the same folder in which the RAR lives.
RarZilla is squarely aimed at those people who predominantly use the RAR format, but I'd like to see the program support more formats before bestowing higher praise. I can't think of anybody who uses only one kind of archive exclusively. Fans of other formats should look elsewhere for an extractor or a dual-purpose archiving/unarchiving tool.