I don't joke about the holocaust. I don't use the term Nazi to describe anything (ie. grammar nazi).
I don't joke about sexuality.
I don't joke about race or religion.
I don't like jokes about abuse or violence.

Some of my biggest pet peeves are:

Male Bashing Jokes
Jokes about size (especially when it's larger people picking on skinny people... because that's some how ok because?)

That's about it really.