This thread inspired me to take inventory of the fleet, at least as far as rear derailleurs are concerned (I tend to mix and match FDs for functionality):

1 x Campagnolo Potenza (11 sp)
1 x Campagnolo Veloce (8 sp)
1 x SunTour Cyclone
1 x SunTour Superbe
1 x SRAM Rival
1 x Shimano Deerhead
1 x Shimano Deore LX
2 x Shimano Ultegra
6 x Shimano XTR

XTR is the winner here mostly because of its large-cog and chain wrap capacities and its versatility. I'm running it in 8-speed index setups with Campy Veloce 10-speed brifters, with 8-speed Shimano bar ends, and with friction thumbies. Perhaps not surprising, the two SunTour derailleurs are on the two older vintage bikes in the fleet that aren't running internal-gear hubs.