From the last few years, I'd say it has to be the 'N' word.
(Afraid to type it in case it isn't censored properly on Boards and the Gardai come to arrest me).
It would likely have been the cnut word for many folk, but since I heard it a handful of times in the Oscar nominated 'The Favourite', it seems to be going mainstream.
I watched a news piece the other day about police racism in England since the Stephen Lawrence murder, and a black man actually said something like "back then walking down the street I would have been called the n word".
So its now so offensive that even black people aren't allowed to say the word when explaining a situation. Was this black man afraid that the internet would turn on him for using it??
Will we ever hear the full word uttered again, or is simply going to become "the n word".