You've run some pretty fancy MC's, but the _______ MM cartridge really impressed me

Soundsmith makes great sounding MI cartridges, I'm currently using the Carmen 2 nice all around sound and very ready rebuild prices.

Grado, Soundsmith, Nagaoka and London Decca are all MI. Of those, if londondecca.com don't start making cartridges again, I'd go for the Nagaoka MP-500. I haven't had anything higher than a Grado Statement 3, or a Soundsmith Sussurro MkII, but to my ears the MP-500 knocks their socks off. If the Deccas are made again, that is a step better, but a lot more expensive.

No question, the Technics EPC 100MK4, a conventional MM with super low tip mass and all the details done right. It has more bandwidth than any MC with flat bandwidth to 80 kHz and a resonance of 100 kHz. It wasn't officially imported into America but in the 80s many of the most famous mixing engineers used it.

The problem with selling it was it would have been a $500 MM by a middle hi fi company Technics when exotic MCs had taken over the market and Technics knew no one would buy it.

The Nag MP500 has been superb, and is the best of the MM genre I've own or heard.  

Another vote for Nagaoka, I use the 200. I like it over the zu/denon 103 and the mid-priced AT my buddy has. My plan is to continue up the ladder eventually, I'm in no hurry.