WavPack lossless audio compression. Note that, when converting .wav to this format and back again, the RIFF header is not necessarily preserved losslessly (though the audio is).
this is a lossless-format (and encoding algorithm) for Apple platforms. M4A is widely used in iPod players and as a component in QuickTime media-players. The m4a codecs decoder is found in open sources - this allows third party users to open files in that format.