I have written about the Farmer’s Mill before, it has been successful against all odds and a new and improved version has just arrived.
The farmer’s mill dirties the tone in a way that is hard to explain, it’s not a distortion per se, it’s more like a “broken cable emulator”. I know that sounds weird but it can sound kind of cool. Apparently, Jack White is a fan. I think a video is probably the best way to understand:
Apart from the new Farmer’s Mill, Crushsound has released very cool looking ceramic slides, check them out: