RAR File Open Knife is a little tool that only extracts the RAR format of compressed files. The developer explains that this specialization allow it to be faster and more efficient than the 'Swiss-army knife' tools that decompress anything.
While it's not the most attractive application, RAR File Open Knife is certainly easy to use. Simple drag your RAR file into the app window, and it will be automatically unpacked. Alternatively, you can choose 'Extract!' from the right-click context menu when you click on a RAR file.
You can define a default output folder for your decompressed files, which makes the process faster. Decompressing itself is very fast - whether it's fast enough to stop users choosing a multi format compression program like 7-Zip is another question.
RAR File Open Knife doesn't have any additional options, although the interface is tabbed, with a pretty strange selection of the developer's unrelated downloads available! Despite that quirk, RAR File Open Knife still does its job very well, even if it is a limited application.
If you only want to unpack RAR files, RAR File Open Knife does the job quickly and efficiently, although you may miss the broader options available in other similar apps.