UVI Falcon - Sampler/synth hybrid instrument
Serum - VST for FL Studio, Ableton Live, and many other VST supported DAWs. Heavily utilized in EDM.
Pianoteq - Pianoteq is a virtual piano that runs on your computer.
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.
LinuxSampler - LinuxSampler - free, open source pure software audio sampler with professional grade features.
SynthMaster One - Powerful, universal wavetable synth with an intuitive workflow.