For me, it's Tal Mod. Fantastic analogue sound, plenty of modulation, does hard sync, FM, ringmod, nice unison. MSEG, basic sequencer/arp, simple GUI which is easy to navigate, not too CPU heavy. It's my go to for basic analogue stuff, can do sharp cutting leads, squelchy acid, eerie pads, even pretty nice drums. Downsides are the useless filter saturation which drops volume significantly, ladder filter style bass stealing resonance, and the fx are average (but usable). It's not expensive too. Presets aren't great but it's so easy to program that this hardly matters. I use multiple instances every track. Honestly sounds better than stuff like Diva to me.
Please share your hidden treasures.
