Amadeus Lite is a fully featured wave editor featuring smart editing, automatically preventing the appearance of cracks when performing editing operations. It also allows to paste a sound
over an existing sound, performing a mix and has extensive built-in support for markers, facilitating the navigation in large documents.
Besides having many built-in sound effects, Amadeus Lite comes with full support for Apple's Audio Units. These are sound effects developed by third parties (a few of them are developed by Apple and are built into MacOS X) that allow to extend Amadeus Lite's possibilities without limits. Some free Audio Units can be found here, here, and here.
Amadeus Lite converts audio files from and to no less than 13 sound formats, including AIFF, Wave, Mp3, Mp4, M4a, Ogg Vorbis, WMA, FLAC, and CAF.