IK Multimedia offers a free Memory-V synth rompler. You have to be/become a newsletter subscriber and then install the free version of Syntronik, which the Memory-V is a part of (video instruction). This offer is limited to Feb 26th !
Vital has been updated and now features custom skins amongst other things (For Pro users and subscribers). Vital is a cool wavetable synth for a nice price (80$). Free version available with 75 presets and 25 wavetables.
The Mountain is a free Synthwave subtractive synthesizer for 80s inspired sounds. Needs the full version of Reaktor.
You can get a Moog emulation for free from IK Multimedia if you subscribe to their newsletter until Dec 30th.
DFR-76 is a FREE plug-in that contains 27 HQ playable instruments ranging from bass, keys, plucks and more. Here are some audio demos: