When I was growing up it was my mum with:
"You've always got to have the last word, don't you?"
"Well, no, bacause you field that exact same line EVERY SINGLE FUCKING TIME!!!!"
But I suppose religious people who blindly deny science, people who are dead set against gay marriage despite every argument against it being WRONG.
And from work, "Last of the big spenders" (Which I think I hear on average about once every hour or so. After the first few thousand it's impossible to even fake a laugh, I just look at them like I don't get it), "How else am I going to get it home, magic?" (In response to me asking if they want a carrier bag, like I've just kicked them in the shins and told them they can't prove I did anything, so they'll have to be immediately hostile to me for doing my job.)
EDIT:
Phasmal said:
To which I replied `Fuck shit buggercunts kiss my arse`.
Not a bad display of impromptu swearing. Incidentally, do you have any kind of accent? It would make it considerably more awesome to imaging that being said in, well, any accent, really.