Swedish EMU Referendum
I expected "No" camp to win, but with a tiny margin. First exit polls indicated that I was right. But the final result put "No" in much wider lead – all that despite speculations about sympathy for murdered Anna Lindh and high turnout giving the huge boost to "Yes" camp.
In the end, Swedes were drawn to the polls, but in the actual boots they voted with their minds rather than with their hearts. Sympathy can't win votes, at least not in well-established democracies.
On the other hand, I think that at least a fraction of voters was embarrassed to admit that they voted "No". That would explain discrepancy between exit polls and actual referendum results.