Two of mine.
One when I was in the equivalent of "High School". My spanish teacher lived in South America for years, and had the foulest mouth of anyone I've ever met ... at least when speaking spanish
e.g if a student was talking while he was, he might say "Callate la puta boca, tonto. Chingar, chicos...estoy hablando!"
A few yeas ago when I first started college, we had an amazing lecturer. Really good at what he did, really entertaining. MAde the subject come to life.
Midway through the year, he was able to get us all to say, on command and in unison, "Fuck off and die".
"You can do this in PHP and get away with it, BUT . . . what would Java say!?"
"FUCK OFF AND DIE!"
And he'd double over and laugh at the stupidity of the whole situation. It was great
Also, I often forget that people can get offended by casual swearing. Everyone swears constantly in Ireland.
Obviously directing it AT someone is serious, but casual discussion? No biggie. If you're offended by it in Ireland, people tell you to "grow the fuck up and get over yourself"
Or, more probably, "Pffft, fuck off"