Behringer Proton

It's basically two great sounding analog synthesizers in one. The versatile dual oscillators sound great with either the Proton's filters or through a Moog-y ladder filter. Envelopes are fast (or slow if you want them to be), the filters are multimode with a setting that tames the filter drive, I think, and makes the resonance smoother. The wave folder works pretty well with sine and triangle waves and can make some almost guitar-like sounds. It gives you a lot of functionality for a decent price and is the multitool in my modular case.

I had tuning issues at first, until I read the manual and did the calibration a few times (hold para and ASR retrig). Now I run the calibration every time after a short warm up and the tuning is pretty stable.

The knobs on mine have started to crack, they're very slippery and poor quality and most of them don't even have the pointer marking on top, so it's almost impossible to see where some controls are set. I intend to replace them for something grippier.