Dexed - Dexed is a multi-platform, multi-format plugin synth that is closely modeled on the Yamaha DX7.
Serum - VST for FL Studio, Ableton Live, and many other VST supported DAWs. Heavily utilized in EDM.
Surge XT - Open-source subtractive-hybrid synthesizer formerly sold commercially as Vember Audio Surge.
Omnisphere - Piano, pad and synth VST for DAW's.
Synth1 - Synth1 is a software synthesizer. Functionally it is modeled on the Clavia Nord Lead 2 Red Synth.
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.