Dim mak is a very controversial topic. There are undisputably striking points that can cause pain and KO's - but not nearly as reliably as some (like in this video) would have you think. Check the Pressure Point forum here for some much better info.
Chi balls are not even controversial to me. They simply do not exist, at all.
"In case you ever wondered what it's like to be knocked out, it's like waking up from a nightmare only to discover it wasn't a dream." -Forrest Griffin