Shimano XTR M952, long cage.
For friction or indexed, it works great. Got a nice light action, so it works with Simplex levers. Can probably work with bigger than 34t cogs using one of those drop-down link things. Reasonably svelte at 210g or so. Sealed ball bearing pulleys - even the centeron pulley has ball bearings in it, which slide side to side. Brilliant mech.
I have one on my Trek (shifted by retrofriction barcon), on my Colin Laing tandem (shifted by Shimano indexed for 9), and on my Ron Cooper (shifted by Suntour levers).