QPR 2012 without a shadow of doubt.
The game lifted the club beyond quirky investment story to one with emotion, drama, rivalry in front of a world wide audience. I live in the US, and for many over here, that is when we first came to their attention.
Lifted a 44 year monkey off our backs, shifted the balance of power not just in Manchester but in England. Elevated the club to a new confidence level that has incredibly been maintained for another 11 years and counting..
If I was being cynical, I would also suggest that this is when the 'real' negativity in the media fanned by the displaced 'history clubs in red' truly began .. before that day it was all about bad Berts in bed sheets and a bit of a laugh