Dexed is a synth plugin based on the Yamaha DX7 synthesizer. It is available for Windows, Linux and Mac as a VST, AU, or LV2.
GitHub pagePictured here in Reaper
Like many soft synths, Dexed has many UI elements designed to look analog. One nice touch is that it displays ADSR graphics on many of its controls for visual feedback, and it also includes a virtual MIDI keyboard on its display. Dexed comes with 32 presets.