CasterSoundboard - A soundboard for hot-keying and playing back sounds. (For podcasting)
Serum - VST for FL Studio, Ableton Live, and many other VST supported DAWs. Heavily utilized in EDM.
JN Soundboard - An open-source hotkey soundboard program
Korg Legacy Collection - Korg Legacy Collection is a suite of VST instruments that acts as an audio plugin software for integrating synthesizers and effects units into your digital audio workstation.
Soundplant - Play sound files with the computer keyboard
SynthMaster One - Powerful, universal wavetable synth with an intuitive workflow.