For me it's generally anything about:
violence
smacking children
animal cruelty
abuse
rape
suicide
mental illness
disability
race
gender
sexuality
domineering wives (the ball and chain stereotype)
My BIL loves to make un-PC jokes. He thinks he's the next Chris Lilley, as though anything that is obviously un-PC is funny. He is so NOT funny and doesn't have Chris Lilley's sense of irony. I can't stand all his stupid "jokes". He just sounds like a sexist, racist, homophobic shumck most of the time.
While I don't personally use words like retard, gay (as a put down) or the c words, they don't instantly offend me if used by a person in a context that I know is not intentionally offending those that the words refer to IYKWIM.

