... is the modified Pittsburgh Oscillator (or actually, two of them...).
I think Pitts gets a raw deal from people because they are inexpensive, and (thanks to the Foundation systems) tend to be the first thing that people get. But some of their modules are best-in-class pieces; people rave about the Filter module, and I think that the Oscillator is, along with the Tiptop Z3000, in a race for 'best sounding sawtooth-core oscillator'.
So what is so hot about my modified Oscillator? Well, I had a nice talk with Chris Blarsky (of Ninstruments fame...) about how I liked the sound of this oscillator, but I didn't really care for the difficulty I had with precise tuning - especially in a live context. I showed him the board layout, and asked about doing a mod where there would be a 10-turn pot instead of the standard 270-degree pot.
He thought about it for a minute, then said "Sure". I was going on a business trip, and he started cranking. Partway through the trip, he calls me up and says: "Um, with the 10-turn pot in there, it doesn't seem like the fine tune knob does much. Do you think there is something that could work better? I thought back to my experience with the 5U Q106 (my fave oscillator ever...), and said "Octave switching!". So now, in addition to the 10-turn tuning, I have an octave switch - a perfect addition for a live rig.
One thing that people say is "I need to do dive bombs - how could that happen with this setup?". Well, apart from wanting to scoff at dive bombs, I'll say that Chris managed to find some very light-touch 10-turn pots. I can easily put my index finger on the edge of the knob and spin in all 10 turns in an eye-blink. I've had other 10-turns that were super stiff, so I can understand the question. But somehow, Chris nailed this one, and I've got the best sawtooth oscillators I can imagine!