Serum - VST for FL Studio, Ableton Live, and many other VST supported DAWs. Heavily utilized in EDM.
ReSlice - Slice your audio with an advanced, rhythmic arpeggiator and FX.
Surge XT - Open-source subtractive-hybrid synthesizer formerly sold commercially as Vember Audio Surge.
Auxy Music Studio - Auxy brings real music creation to iPhone in a simple and inspiring format.
Vital - Vital is a spectral warping wavetable synthesizer with drag'n'drop modulation workflow and animated preview of the synth's inner workings where needed. Comes with many modulation sources (including audio-rate), MPE support and FX chain.
nlog Synth - Professional Virtual Analogue Synthesizer ::: check nlogmusic at YouTube :::