Magix SpectraLayers - SpectraLayers Pro transforms sound into a unique visual world of multidimensional audio data.

JN Soundboard - An open-source hotkey soundboard program

Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.

CasterSoundboard - A soundboard for hot-keying and playing back sounds. (For podcasting)

GarageBand - GarageBand is a fully equipped music creation studio for Mac

Soundplant - Play sound files with the computer keyboard