There is only one file type that uses the .WAFF extension:
Internet Explorer for Mac Web Archive
Web archive file format (WAFF) used by Internet Explorer for Mac to store a collection of webpages, along with associated images and linked pages up to 5 levels deep.
Internet Explorer for Mac can open WAFF files but it is not supported by OS X. However, there are several programs available that will assist you in opening your WAFF files. The WebArchivConverter utility (available for OS X 7.5 - 9.2.2) enables you to convert WAFF files into iCab web archives and the WAFInspec program (available for OS X 10.2.5 and later) can be used to browse, preview, and extract WAFF files.
Updated: July 22, 2015