Hhhm, interesting thread this!
As a chemic, and a young one at that as I missed all the halcyon days of King Kurt, Offiah Davies etc, and back to back title wins, it is Warrington. I think I speak for most Widnes supporters. If not all. Though you may find a few oddballs who claim it is Hull FC or Leeds etc.
A good majority of Wires fans I speak to have always maintained it is Wigan though. Even those who were there in the good old days of Wildernesspool. I think that maybe has something to do with the relatively close proximity and the fact that Wigan and Warrington, as towns are probably more equally matched and populated than Widnes and Warrington. I don't really see how Stains can be classed as Wires major rivals though, iMHO!
Anyway, roll on 2012 (hopefully) when I can have a WWF style handicap match vs wire 85 and Latchfordbob outside my old Maths room on the Wad forecourt.