My favorite has to be the baby seal post. I don't even remember what was said, I just love that people were shocked. Nowadays I kind of look down at shock humor, it just seems too easy to make.
There is a subreddit on Reddit all about very offensive comedy(they mostly just say the N-word) that I unsubscribed to a while ago and last I heard they were making jokes about the Connecticut shootings and that just fucking disgusts me. I know kids that go to elementary school and the thought of that happening to them, just saddens me beyond belief.
/b/ should stay on /b/. I use 4chan pretty often, but I stay on the work-safe boards and even then there is just too many people being "edgy".